Abstract: An in-plane position sensor detects positions along two directions or X-Y directions to produce a pair of position signals concurrently. The pair of position signals controls control parameters which influence upon a variety of effecters and addition processor which are implemented in a digital arithmetic unit (DSP).

Abstract: A high pass filter 32 having a cut-off frequency of 200 Hz and a cut-off response of +12 dB/OCT and a low pass filter 33 having a cut-off frequency of 400 Hz and a cut-off response steeper than ?24 dB/OCT are used to pick out components in a double overtone region of 200˜400 Hz of a bass musical instrument such as a base or a bass drum from an input audio signal. The component which is picked out is input to distortion applying means 34 having an input-output response which is a non-linear response having no point symmetry with respect to 0 point, thus applying a distortion to cause even-numbered overtone components to be produced. An output from the distortion applying means 34 and the input audio signal are summed in a summer 18 to be delivered. Natural tones which have boosted bass tones and which are free from impurity are obtained.

Abstract: The vibration of a vibratory element, caused by applying thereto a shock, is detected by a vibration sensor and provided as an electric shock signal to a resonance circuit. The resonance frequencies and resonance decay time of the resonance circuit can freely be adjusted. By setting the resonance frequencies and resonance decay time of the resonance circuit to arbitrary values, desired frequency components are extracted from the electric shock signal and output as a sound signal of an electronic musical instrument.

Abstract: Left- and right-hand keystroke windows X.sub.L and X.sub.H are decided in accordance with the positions of player's left and right hands pressing keys. When the number of pressed keys in either one of the windows X.sub.L and X.sub.H are larger than a predetermined value, that window is decided to be used as a chord identifying window, and on the basis of a combination of pressed keys in the chord identifying window, an accompaniment chord is decided for automatic accompaniment.