Keyboard expression often shortened to expression is the ability of the keyboard of a keyboard instrument to respond to the dynamics of the music.

For example, the piano responds exceptionally well to the force with which the keys are initially pressed; It is velocity sensitive. Several of its predecessors, such as the harpsichord, were less velocity sensitive than the piano, which is one of key the advantages of the piano.

The clavichord and some electronic keyboards also respond to the force with which a key is held down after the initial impact; They are pressure sensitive. This can be used by a skilled clavichord player to slightly correct the intonation of the notes, and/or to play with a form of vibrato known as bebung.

There is some confusion relating to the term pressure sensitive, with some using it as a synonym for velocity sensitive. To avoid this confusion, pressure sensitivity is sometimes called aftertouch.

Both velocity and (true) pressure sensitivity are supported independently by the MIDI standard.

In general, only the top of the line electronic keyboards implement true pressure sensitivity, while most (not all) recent electronic keyboards support velocity sensitivity. This has led to an unfortunate tendency for manufacturers and distributors of some inferior keyboards to describe their purely velocity sensitive instruments as pressure sensitive.