Keyboard expression

As Aftertouch refers to electronic keyboard instruments such as synthesizers, keyboards, an additional key function. Thereby continuously further signals are generated by a stronger or weaker pressing the button after the actual keystroke that can be used to effect control or pitch change.

Especially the use of MIDI devices it is between Channel Aftertouch (also mono aftertouch) and polyphonischem aftertouch to distinguish. If just the talk is of " aftertouch ", the Channel aftertouch is usually meant.

When Channel Aftertouch a single signal value for the entire channel will be used. When polyphonic aftertouch in addition to the normal aftertouch value, the note is included in the signal.

Example: The Aftertouch a tremolo effect to be triggered. When Channel Aftertouch the sounds of all currently held keys begin to quaver, when you press one button stronger. When polyphonic aftertouch, however tremolieren only the sounds that are on the actually stronger pressed keys. Thus it would be possible for example to play with the left hand chord accompaniment without tremolo and a melody with the right line in which one emphasizes individual tones selectively with the tremolo.