Abstract: Exponential and pseudo-exponential decay function values are generated by scaling a fractional decrease per sampling period by a previous decay function value and then subtracting the scaled fractional decrease from the previous decay function value. In one embodiment, a multiplier multiplies the fractional decrease by the previous decay function value and provides a product signal representing the scaled fractional decrease. An adder subtracts the scaled fractional decrease from the previous decay function value. In another embodiment, a shift block replaces the multiplier and approximates multiplication by a binary shift of the fractional decrease. The size of the shift is determined by the previous magnitude of the decay function as indicated by a priority encoder. Shifting generates a pseudo-exponential decay function which is suitable for music synthesis and can be generated quickly using less expensive hardware.

Abstract: Synthesizer models for emulating musical instruments can be improved using an analysis model that compares the output signal of the model to a recording of a desired sound and derives a residual signal that can be used to correct the model. When the original model is a good one, the residual signal is small and takes much less memory to store than is required for a sampled sound.

Abstract: A circuit is provided for filtering asynchronous metastability. The circuit includes two or more output lines that provide signals indicative of the assertion of control or data input signals at a plurality of input lines. Despite the simultaneous assertion of two or more input signals, the circuit prevents the simultaneous assertion of more than one output signal, thereby preventing adverse effects within a digital system connected to the circuit.

Abstract: Synthesizer models for emulating musical instruments are improved to take into account sympathetic string vibrations. One embodiment of the present invention scales an output signal from a sound synthesis model and uses the scaled signal as an input signal for a number of single-string emulations causing the single-string emulations to produce sound signals corresponding to sympathetic string vibrations. The output signals from the synthesis model and from all of the single-string emulations are added together. Another embodiment employs an octave's worth of single-string emulations to emulate the lower strings of an emulated instrument. Still another embodiment is a synthesizer which includes an input bus for accepting a sound signal, scaling means, a plurality of single-string emulations, and means for summing output signals from the string emulations. Embodiments preferably employ waveguide synthesis or the plucked string model to emulate single-strings.

Abstract: An anti-clipping mixer circuit is provided within an integrated circuit. The mixer circuit allows for the independent level control of each input signal, thereby allowing the optimization of the signal-to-noise ratio. A master level control is provided to limit the overall combined output signal to a level below the operational amplifier's maximum voltage level. A control circuit may be used to automatically adjust the input signal levels as well as the combined output signal level.