Keyboard expression
Baroque-style clavichords and professional synthesizers are aftertouch-sensitive—applied force on the key after the initial strike produces effects such as vibrato or swells in volume.
The piano, being velocity-sensitive, responds to the speed of the key-press in how fast the hammers strike the strings, which in turn changes the tone and volume of the sound.
The volume of the note can be changed by striking harder or softer, and the pitch can also be affected by varying the force of the tangent against the string.
By applying a rocking pressure up and down the key with the finger, a performer can slightly alter the vibrating length of the string itself, producing a vibrato quality known as bebung.
On some keyboards, sounds or synth voices have a preset pressure sensitivity effect, such as a swell in volume (mimicking a popular idiomatic style of vocal performance with melodies) or the addition of vibrato.
Small tabletop organs and accordions often respond similarly, with sound output increasing as keys are pressed further down.
Even the small circular accompaniment ("one button chord") keys found on accordions and on some organs exhibit this phenomenon.
Accordingly, some electrically actuated organs have retained this form of keyboard expression — a 34-rank organ in the Swiss village of Ursy is equipped with hi-tech features from Syncordia, including what some erroneously claim is the first non-mechanical action that directly controls the opening of a pipe organ's pallets in direct proportion to key movement, ostensibly combining the virtues of electric action with the intimate control of tracker action.
Thus a displacement sensing keyboard may be better at providing both organ and piano feel in a single keyboаrd controller.
Most digital pianos implement a displacement-sensitive keyboard, in order to simulate the sound-stopping length of the note after the key is released.
On an acoustic piano, releasing a key after being partially depressed will result in a quieter, shorter sound stopping.
The VK-9 digital organ, for example, offers a proximity-sensitive detector that triggers the Leslie speaker, a ring modulator, or other effects.
