Abstract: This invention is a display system for measuring and displaying, individually or simultaneously, the frequencies contained in a musical sound. A transducer coupled to the sound source produces an electrical signal representing the musical sound. The system receives the signal and separates and measures the frequencies of the individual tones comprising the sound. The measured frequency values are displayed as the frequencies themselves or as deviations from target frequencies. The system can utilize a local transducer with the display system or a remote transducer coupled to the sound source.

Abstract: This invention is a display system for an automatically tuned stringed instrument displaying, individually or simultaneously, the frequency of each string of the instrument. The system provides for using the display to manually tune the instrument or to initially tune the instrument to within the operating range of the automatic tuning system.

Abstract: Apparatus for tuning a stringed musical instrument includes an electronic tuner circuit and a visual display located in either the pickguard or the pickup mounting ring of the instrument.

Abstract: This invention is a display system for an automatically tuned stringed instrument displaying, individually or simultaneously, the frequency of each string of the instrument. The system provides for using the display to manually tune the instrument or to initially tune the instrument to within the operating range of the automatic tuning system.

Abstract: Single and multiple disc strobe tuners employ microprocessor controlled stepper motors for driving the disc(s) to facilitate the use of customized tuning schemes, such as unequal temperaments and stretch tuning. The tuning schemes are stored in a look up table and may be programmed by the user. The single disc embodiment preferably employs an auto note detector which determines the identity of a note being played by an instrument, and causes the microprocessor to adjust the speed of the stepper motor almost instantaneously to a speed assigned to that note in accordance with a selected tuning scheme. This enables a user to play through a series of notes rapidly to verify whether they are in tune with the selected tuning scheme. The multiple, preferably 12, disc embodiment employs a separate stepper motor and micro controller for each disc to accommodate individual tuning of each disc relative to one another.

Abstract: A tuner for stringed musical instruments which has a transducer pickup for converting sound vibrations of the strings to electrical signals and a body being either hollow or solid with a front and back surface and a edge surface extending between the front and back surface. The tuner has a tuner circuit attachable to an interior of the sound box with an input couplable to an output of the transducer and a digital display positionable on one of the edge or front surfaces of the body so that it faces a player when the instrument is in a playing position.

Abstract: The invention is a control system for automatically tuning a stringed musical instrument with a capo installed, using an original calibration function or closed-loop tuning system for the instrument without the capo. The control system uses a capo scale factor which scales frequencies measured with the capo installed to what they would have been without a capo. The control system enables a musician to quickly tune an instrument after installing a capo, in a manner unlikely to be noticed by an audience.

Abstract: Tuner apparatus for tuning an electric stringed musical instrument includes a pickup in a pickup cavity formed in the instrument. A pickup ring extends around the pickup and includes a pickup ring wall forming a visual display panel. Tuner circuitry includes a flexible printed circuit strip adjacent to the pickup and positioned in the pickup cavity. The flexible printed circuit strip is electrically connected to a light module positioned next to the visual display panel of the pickup ring.

Abstract: An electronic musical instrument comprises a tone generator for generating a plurality of different digital waveform signals corresponding to different timbres, and a device for setting a plurality of ranges defined by two parameters, a first one of the parameters being a pitch parameter and a second one of the parameters being a key touch parameter. The parameters vary according to the musical performance, and a range for the pitch parameter in combination with a range for the key touch parameter respectively designating one of the plurality of different digital waveform signals having different timbres. An input device is provided for inputting the two parameters according to a musical performance.

Abstract: This invention provides a control system for automatically tuning a stringed musical instrument, utilizing a library of calibration functions to tune the instrument in a plurality of operating conditions without recalibration. The operating conditions can include changes in temperature and humidity, different sets of strings made with different materials and gauges, broken strings and the installation of a capo. Calibrations can also be provided for instruments of different makes and models, string lengths, body materials and actuator types. The control system is adapted for use in a stringed instrument having actuators attached to each string for changing the frequency of the string in response to a control signal. Each calibration function relates the frequency of a string to the actuator position of that string. The invention further provides an automatically tuned stringed instrument using the control system, and a method for tuning a stringed instrument.

Abstract: A method is specified for pitch recognition, in particular for musical instruments which are excited by plucking or striking, in the case of which method the interval between zero crossings of a signal waveform of an audio signal is used as a measure for the period length of the audio signal.Reliable pitch recognition is intended to be possible in a simple manner using such a method. The method is intended to be capable of being implemented with a low level of computation power.To this end, the magnitude of the gradient of the signal waveform is in each case determined in the region of its zero crossings, and the magnitude of the gradient is used as an assessment criterion for the selection of the zero crossings to be evaluated.

Abstract: A musical instrument tuning aid. The display provides the user tuning information in a rapidly interpreted form. The input note, or tuning device setting, is displayed in a clock face format. A sharp/flat indicator provides a course display for gross tuning. A display means for electronically producing a stroboscopic display between the input tone and the internally generated reference frequency provides for very accurate fine tuning with instantaneous response to pitch changes. Signal conditioning to control signal level enhances the strobe display. Tracking low pass filtering is provided to enhance strobe display for high harmonic content signals. An adjustable band pass filtering mode is provided to allow analysis of individual harmonics. A crystal timebase is used to generate a high accuracy reference frequency with fine calibration adjustment.

Abstract: A tuning system is described for automatically tuning a musical instrument having adjustment means for changing the frequency of a musical tone produced by a musical string of the musical instrument. The tuning system of the present invention is useful with respect to a wide variety of musical instruments, e.g., string instruments such as, guitars, harps, pianos, etc., and other instruments. A tuning system is operative to selectively tune a musical string of a stringed musical instrument to a user selected predetermined frequency value.

Abstract: A stringed instrument with an on-board tuner which detects vibrations of the strings and determines and displays the identity of the string which is being played and the deviation of the string's pitch relative to an in-tune reference pitch. The tuner display is situated such that it is not readily visible to casual observers, such as an audience, yet is oriented such that the musician can easily view the tuner display from a normal playing position. In the case of an electric stringed instrument, the display is inlaid in the top surface of the neck of the instrument near the instrument's body. In the case of an acoustic stringed instrument, the tuner is mounted inside the body of the instrument and is visible through the sound hole. The instrument is provided with a strap assembly which attaches to a balanced pivot point on the instrument and provides a single connection which serves as both an electrical connection to the amplifier and a mechanical connection to the strap assembly.

Abstract: A fully adjustable acoustic guitar bridge is claimed that allows the strings (nylon or steel) of an acoustic guitar to be separately and continuously intonated accurately and easily whenever necessary. The bridge system employs a minimum of alterations to the traditional non-adjustable acoustic guitar bridge to retain the acoustic qualities of the instrument. Recessed, rear-loaded cap screws utilize the forward pull of the guitar strings to stabilize the adjustable saddles. A threaded saddle capture on each saddle provides stability, continuous threading capability, and the freedom to use acoustically resonant materials (bone, phenolic, composites, etc.) for saddles. These features eliminate the need for springs or other fasteners, which would have a negative effect on the acoustic guitar's tone and sustain. A rosewood shim is employed on acoustic/electric guitars over the internal bridge pickup.

Abstract: A chromatic tuner display is provided for indicating a relative difference between a pitch of a sound and a pitch of a desired note of a musical scale. The display comprises a base member, a predetermined point on the base member corresponding to the pitch of the desired note, and a colored light arrangement for visually representing the pitch of the sound. The colored light arrangement is mounted on the base member and includes a plurality of illuminative letters corresponding to notes of the musical scale, and a plurality of additional illuminative characters positioned on the base member between adjacent letters corresponding to sharp and flat variations of the notes represented by the letters. An illuminated letter or an illuminated letter and character combination represents the desired note.

Abstract: A chromatic tuner display comprises a base member, with a predetermined point on the base member corresponding to the precise pitch of a desired musical note.

Abstract: A method for measuring dynamic hardness of elastic materials is applied particularly to determining the state of tonal quality for a piano hammer. The method includes selecting a piano hammer of predetermined type from a set of piano hammers, causing the selected piano hammer to strike against an impact surface having the form of a piano string or string grouping appropriate to a piano hammer of the predetermined type, measuring one or more elements of force and motion of the piano hammer striking the impact surface, e.g. force, determining, e.g., the cut-off frequency of the power spectrum for the selected piano hammer striking upon the impact surface, and comparing the determined cut-off frequency of the power spectrum for the selected piano hammer against a predetermined range of cut-off frequencies of power spectrum acceptable for piano hammer of the predetermined type. An apparatus for testing is also described.

Abstract: An electronic tuning device has selectable width tuning ranges wherein selected pairs of the LEDs in a single row of LED's are activated, such as being turned on, blinked or flashed, so that the spacing between each activated pair of LEDs indicates the width of the tuning range during a range indicating mode. The sensing of a fundamental frequency of an input tone causes the operation of a corresponding LED in the row of LEDs to indicate the nearest note along with in-tune and out-of-tune conditions.

Abstract: Apparatus (1) for varying the pitch of the strings (12) of a guitar (15) comprises a respective adjusting mechanism (10) for each string. This mechanism includes an externally threaded tubular member (20) within which one end of the string (12) is secured. Tension is applied to the string by a coil spring (124) which has one end fixed to the tubular member (20). A drive motor (34) is arranged to rotate a gear (26) whereby longitudinal movement of the tubular member (20) is effected to vary the tension in the string (12). The rotation of the drive motor (34) is effected by an electronic circuit arranged to tune the pitch of the string a reference.

Abstract: A CPU measures the interval between the zero-crossing points at the two ends of a waveform element a having, e.g., a positive polarity. Thereafter, the CPU sequentially measures the interval between the zero-crossing points at the two ends of each of waveform elements b, c, and d having the same polarity. Upon detection of the waveform element d which is almost equal in interval to the waveform element a and is located nearest thereto in terms of time, the interval between the start points (zero-crossing points) of the waveform elements a and d is extracted as the pitch period of the input waveform. Subsequently, the above-described series of operations is repeated.

Abstract: An automatically tuned musical instrument provides a means for keeping strings under tension in proper tune. It also provides a mechanism to simplify installing new strings on the instrument. The tuning system includes a magnitude comparator to eliminate crosstalk which can result in improperly tuning one string when receiving a tone from an adjacent string. The system tensions a string or a plurality of strings at fast speed to within a whole tone or their desired frequency and then fine tunes the strings to desired frequencies. The mechanism includes a guide canal for each string to guide the string into pinch rollers and a flexible conduit to guide the string onto a guide reel to provide an easy, sure way to install strings onto the instrument.

Abstract: A device and method for very rapidly and accurately tuning each string of a guitar by contacting the string perpendicularly in order to change the tension in the string. The device is located at a position between the bridge of the guitar and the end of the guitar string. A tensioning member consisting of a shaft and disk is located perpendicularly to each string. The disk has a string engagement means which contacts the string. The tensioning member is connected to a stepping motor. The stepping motor causes the tensioning member to displace axially. The vertical movement of the member causes the disk to contact the string perpendicularly and change the tension in the string, causing the string to become tuned.

Abstract: A method and apparatus for tuning a musical instrument. Measurements are made of the inharmonicities of three notes (e.g., F3, A4 and C6 in a piano). One of the notes (e.g. A4) is a standard note that is to be tuned to a standard frequency. The measured inharmonicities of these notes determine a slope of a tuning curve and a position to intercept the standard note frequency according to the following: ##EQU1## Y(p,N) is the cents deviation relative to the equally tempered scale of partial p of note N, F is a factor by which the inharmonicity increases per octave taken from the measurement, B(N) is the inharmonicity of note N, and B(STD) is the inharmonicity factor of a standard note (e.g., A4 at 440 Hz).

Abstract: An electronic music system for computer-controlled interactive practicing and learning to play a guitar includes a transducer which is detachably securable to the guitar and generates analog signals representing the playing of the guitar, an interface for converting the analog signals to computer-processable digital signals, and a computer for receiving and processing the digital signals. The system uses a communication protocol which employs time stamping of data to permit use with ordinary guitars but without high speed frequency determination. The computer provides audio and video outputs including staff and guitar fingering representations of notes, chords, scales, compositions, and like musical structures, both to teach the user and suggest music to be played by the user and to illustrate what the user has played. The system is operable in several modes which may be controlled by the user by signals produced at the transducer.

Abstract: The present invention enables accurate measuring and regulating operations to be carried out by measuring with a rule the quantity of movement of a hammer in a grand piano during an action mechanism regulating operation for attaining the normal striking of wires with the hammer. The wires S provided in a tensed state are held between the lower surface of a mount 4 and a locking rod 3 on a measuring tube 2 pressure-contacting the same lower surface, and the lower end of a measuring rod slidingly moved in the measuring tube is placed on the top end of the hammer, the quantity of movement of the hammer being then read directly with reference to the relative positions of a scale mark 8 shown on the measuring rod 1 and the upper end of the measuring tube 2.

Abstract: A method of automatically and instantaneously shifting the musical scale of a piano is constituted by the steps of gradually changing the tension of the strings or the length of a vibrating portion of strings of the piano for changing the tone of the tension adjusted or vibration length adjusted strings in order to shift the musical scale of the piano to another desired musical scale, simultaneously applying mechanical vibrations to the respective strings at the same frequency as the frequency of the tones required for the respective strings to obtain the desired musical scale, detecting the resonance of the respective strings, and when resonance of the respective strings is detected, discontinuing the change of tension or change of length of the vibrating portion of the strings and application of the mechanical vibrations.

Abstract: Automatic tuning control arrangement for a string musical instrument, such as a guitar, has a pivoted tone arm with a hook at one end for attaching to an associated one of the guitar strings, and a shape memory metal wire tension motor extending between the tone arm and an anchor point on the instrument to rock the tone arm in opposition to the tension of the musical string. A strain sensor, such as a strain gauge, is mounted on the tone arm and it is electrically coupled to a control circuit that supplies a control current to the shape memory metal wire in the traction motor. A biasing spring can also be coupled between the tone arm and a bias anchor on the instrument to apply a spring bias in opposition to the musical string tension. As the guitar string or other string stretches over time, the traction motor will rock the tone arm to take up the slack and maintain an even tension on the string, thus keeping the string in tune.

Abstract: A system for tuning pianos and other string instruments utilizes a clamp-on probe with a feedback loop to induce a controlled vibration of the string and its natural frequency of vibration. This frequency is electronically compared to an accurate reference frequency. An associated electronic circuit controls an electric motor driven mechanism which adjusts the string tension until the correct frequency is achieved.

Abstract: A digital signal processing apparatus is provided for identifying the octave, note and cent of a musical sound. The apparatus includes a transducer for converting the musical sound into an electrical signal, a plurality of digital detection units, each dedicated to a particular sub-scanning interval within an overall frequency interval to be scanned, receiving the electrical signal from the transducer, for determining the octave, note and cent of the musical sound by detecting a fundamental frequency of the electrical signal; and a display unit, responsive to the detection unit, for displaying the note as an alphanumeric character and the cent as a positive or negative decimal integral number from -49 to +50 with zero cents representing perfect concert pitch.

Abstract: The string tensioning apparatus includes a string tensioning device to provide the mechanical string tension control function and associated control electronics to regulate the operation of the string tensioning device. The string tensioning device includes a bidirectional motor as the mechanical means to vary, control and maintain string tension. The associated string is directly connected to the motor shaft, whose rotation is regulated by the associated control electronics. A transducer is used to measure the frequency of operation of each string. The measured frequency is then compared to a value stored in memory to produce an indication of the difference between the actual and desired frequency of operation. This difference is then used to control the direction and amount of rotation of the motor shaft to bring the string frequency of operation into compliance with the stored frequency value.

Abstract: A tuning apparatus for a keyboard musical instrument, having a load applicator for applying a load of a predetermined value to a string set up in place, a calculating device for calculating a deviation between a displacement value of the string produced when the load is applied to the string and a preset value of displacement predetermined to give a required frequency of vibration, and a rotating device for turning a tuning pin until the deviation calculated by the calculating device is reduced to zero.

Abstract: In an electronic tuning apparatus used in electronic stringed instruments such as an electronic guitar, an electronic violin, and so on, at least one string is extended along the fingerboard. Prior to picking performance, a present state of the extended string is examined through picking said string. Preferably, a reference pitch data extracted through the string-picking manipulation is stored. During a live picking performance, a performance-pitch data extracted is converted into a data for defining a properly-tuned sound-frequency in accordance with said extended string state. A musical-tone having a corresponding sound frequency is generated based on data for defining said sound frequency.

Abstract: A tuning system is described for automatically tuning a musical instrument having adjustment means for changing the frequency of a musical tone produced by the instrument. The tuning system is useful with respect to a wide variety of musical instruments, e.g., stringed instruments such as guitars, harps, pianoes, etc.; horns; and other instruments. The tuning system is capable of automatically tuning all strings of a stringed instrument simultaneously.

Abstract: A tuning apparatus comprises a piezoelectric element provided on a tuner case, and a mounting member which enable the tuning apparatus to be mounted on a musical instrument to be tuned. The piezoelectric element converts vibration provided by the musical instrument through the tuner case into an electric signal, and outputs the electric signal to a pitch calculation circuit. The tuning apparatus prevents the detection error due to a harmonic component having a larger amplitude than that of fundamental wave component by making the resonance frequency of the tuner case lower than the frequency of the lowest note of the musical instrument to be tuned.

Abstract: A musical tone generating device generates musical tones of a frequency in accordance with pitches which are extracted from input waveform signals by a pitch extracting means. When a pitch extracted by the pitch extracting means varies within a range of a predetermined musical interval difference, an average of the currently extracted pitch and the previously extracted pitch is calculated and the frequency of the musical tone is defined on the basis of the calculated average which serves as a current pitch. On the other hand, when the currently extracted pitch exceeds the above-mentioned range, the frequency of the musical tone is defined on the basis of the currently extracted pitch. In this manner, an undesirable influence to the sound frequency caused by any unnecessary variations or fluctuations in the pitch is decreased or eliminated, thereby enabling producing of a steady sound frequency.

Abstract: A tuning system is described for automatically tuning a musical instrument having adjustment means for changing the frequency of a musical tone produced by the instrument. The tuning system is useful with respect to a wide variety of musical instruments, e.g., stringed instruments such as guitars, harps, pianoes, etc.; horns; and other instruments. The tuning system is capable of automatically tuning all strings of a stringed instrument simultaneously.

Abstract: An automatically operated tuning indicating system for the preliminary tuning and for retuning during the performance of a set of timpani drums or other percussion-type instrument having a tunable resonating body cavity is provided. Automatic indication of tuning is achieved substantially in silence or at very low sound levels without requiring the production of an audible level of sound that could be readily detected by or distracting to persons in an orchestra other than the timpani player during the tuning and/or retuning. Tuning and/or retuning during a performance is under the visible control of the timpani player both as to which kettle drum of the timpani set or other musical instrument is being tuned and the extent of the tuning.

Abstract: A tuning indicator is disclosed in which the octave, note within the octave, and a tuning error is displayed for a musical tone played into a microphone. A bank of digital octave filters, a bank of digital note filters, a bank of digital cent filters operate simultaneously and in parallel to analyze the fundamental frequency of the musical tone. The filters operate by computing the autocorrelation function of the input signal and then performing a Fourier transform to obtain the frequency analysis data. An efficient and simple implementation is disclosed for the computations including the analog-to-digital signal conversion, the computation of the autocorrelation function, and the Fourier transform.

Abstract: A transducer receives notes from a musical instrument and converts them into a A.C. signals. The signals are passed to a frequency voltage converter which outputs a D.C. voltage representative of the played note. This voltage is converted to a voltage range indicative of the highest octave of interest and is then divided by a D.C. voltage representing true pitch. This division is then representative of the number of cents between the played note and the true pitch.

Abstract: A method and apparatus including electronic circuitry for tuning a musical instrument. When a tunable vibratory or frequency producing element of the instrument is actuated, the oscillations thereby created are converted into an electrical signal. This signal is operated upon to eliminate harmonic components and is visually displayed on a readout device as a frequency registered in units of cycles per second for a predetermined period of time. If the vibratory element is actuated again within the predetermined period of time, the frequency of the new signal will be displayed, and if the vibratory element is not actuated again within the predetermined period of time, the display on the readout device will register zero.

Abstract: A transducer receives notes from a musical instrument and converts them into electrical signals. The signals are passed to filter banks containing filters having passbands in different octave ranges. The filtered signals in each bank are added and translated in frequency to the frequency range of the highest octave of interest. The translated signals are then passed through a plurality of filters each of which is tuned to pass directly the frequency of one pitch in that octave. Indicators are attached to the pitch filters to indicate the presence of a signal passing therethrough. Also, additional indicators may be attached to the octave filters to indicate the octave from which the signal originated.

Abstract: A system for extracting the fundamental frequency or pitch of complex waves such as voice, musical instruments or other audio signals. Separate channels extract the fundamental frequency component when it is present in successively wider frequency bands, the frequency intervals between which are equal or less than an octave. Control signals generated in response to the presence of the fundamental components in any lower frequency channel inhibit each of the higher frequency channels thereby reducing the possibility of an overtone being detected as a fundamental frequency component of the complex wave.

Abstract: A pitch sensor for facilitating more accurate tuning of instruments comprises: a reference pitch pulse generator, a saw-tooth generator, a sensing probe, a probe output amplifier, a modulator, and ouput means. The reference pitch pulse generator further comprises an oscillator, a divider chain, gates, and first and second pulse drivers. According to a specific embodiment of the present invention, the sensing probe is a magnetic probe, the oscillator is a crystal oscillator, the divider chain is a decimal divider chain, and the output means is a speaker. Accordingly, the saw-tooth generator is responsive to the reference pitch pulse generator; the probe output amplifier is responsive to the magnetic probe; the modulator is jointly responsive to the saw-tooth generator and to the probe output amplifier; and the speaker is responsive to the modulator. A feature of the present invention is the use of the saw-tooth generator to drive the modulator.

Abstract: A combined pick and stringed instrument tuning device includes a relatively flat, substantially rectangularly shaped housing having a pick attached thereto and is small enough to be easily held in one's hand. A momentary contact push-button switch mounted on top of the housing controls an electronic tuning circuit by selecting one of several predetermined frequencies from a frequency generator. In one embodiment, the tuning circuit is mounted in the housing so that the tuning device is totally self-contained. Alternatively, the tuning circuit is remotely located and is controlled by a cable connected to the housing or by radio signals. The frequency selected is displayed on the housing and the frequency generator drives a strobe light located near the pick. In another embodiment, a microphone mounted on the housing converts sounds from the string being tuned to a signal which is compared to the preselected frequency.

Abstract: A guitar synthesizer comprises a guitar portion and a synthesizer portion which are electrically connected to each other. The guitar portion includes strings stretched between a nut and a bridge and pickup means for detecting a string vibration for providing a guitar sound signal. The guitar sound signal is applied to the synthesizer portion. The synthesizer portion comprises a voltage controlled variable bandpass filter exhibiting a passband characteristic variable in at least two frequency regions of the guitar sound signal as a function of a control voltage. A frequency/voltage converter provides a control voltage representing the frequency of the output of the filter, to the variable bandpass filter, whereby the passband characteristic thereof is made adaptively and dominantly responsive to the frequency of the fundamental wave component included in the guitar sound signal and the fundamental wave component is extracted with accuracy from the guitar sound signal.

Abstract: An automatic note analyzer is disclosed which automatically generates and displays a note signal indicative of the musical note corresponding to an input signal. The disclosed analyzer operates to measure the period of the input signal on a regular basis. According to one aspect of the invention, the measured period is compared with a predetermined window representative of the expected value of the measured period. Measured periods which do not fall within the predetermined window are rejected. According to a second feature, measured signals representative of the period of the input signal are averaged in order to increase the stability of the analyzer. The disclosed analyzer operates in two modes: an absolute mode, and a transposer mode. In the absolute mode the displayed note value is determined with reference to an absolute pitch. In the transposer mode, the displayed note value is determined with reference to a relative pitch which can be readily adjusted as needed.

Abstract: A pitch detecting system is provided for an electric guitar having an existing electromagnetic pick-up for strings. For the purposes of pitch detection, all the signals from the guitar strings are sensed by means of an auxiliary pickup comprising a substantially planar substrate of nonconductive material which is mounted upon the existing pickup, below the strings. A plurality of conductive coils on the substrate are each positioned in alignment with a different pole piece of the existing pick-up. The auxiliary pick-up provides a signal representing the sound of each string to a string separator, which transmits to its output only the signals from the auxiliary pick-up which has the fastest rate of build-up of its input signal. The single output signal from the string separator is provided to a pitch detector. In the pitch detector, a reference point in each cycle of the input signal (i.e.

Abstract: A hybrid organ is disclosed wherein many of the musical tones comprising the complete musical instrument are produced by wind blown pipes. Other tones are produced by an electronic tone generating system and produced by loudspeakers. The electronic tone generating system is adapted especially for this purpose and includes simplified means for keeping the electronically produced tones in tune with the organ pipes in spite of the fact that the pipes change their pitch with even slight temperature and other atmopsheric changes.