If a (musical
supports aftertouch, it has the ability to process
, or receive
pressure information while a key is being pressed.
This allows the patch programmer to create sounds that morph according to a method of user input that is a much more intuitive than a joystick or a mod wheel.
An example of a non-electronic keyboard that is aftertouch-sensitive is the clavichord. (I wrote clavinet before. Whoops!)