Aftertouch

Aftertouch in a synthesizer is a feature that allows the player to add expression to a sound by applying pressure to a key after it has been struck. Additionally, it is referred to as “channel pressure” or “monophonic pressure.” Aftertouch comes in two flavors: monophonic and polyphonic.

All the keys simultaneously receive monophonic aftertouch, meaning that pressing one key will impact all the notes being played at that moment. The filter cutoff or vibrato depth are two examples of single parameters that are frequently controlled by this kind of aftertouch.

On the other hand, polyphonic aftertouch enables the player to apply pressure to specific keys, allowing each key to affect a different parameter. This enables more expressive and nuanced playing. Given that it requires more complicated hardware to implement, monophonic aftertouch is rare.

Aftertouch can be used to control the vibrato depth, amplitude, and filter cutoff in a synthesizer, among other parameters. Additionally, it can be designated to manage extraneous gadgets like effects processors or other synthesizers. It’s a feature that gives the player more freedom of expression and control, enabling them to sculpt the sound in novel ways.

Not all synthesizers have aftertouch; it is more frequently found in expensive, professional-grade instruments and requires more complicated hardware. Many professional musicians and performers want it, but it’s not a standard feature in most MIDI controllers.