Without the key-off effect, the sound of a digital piano lacks authenticity and expression. When you’re playing a piano piece, the missing details will make your digital piano sound somewhat colorless. However, the key-off function is just one of many sound details that sound generators of modern digital pianos and software pianos take into account. On most digital pianos, you can find all of these settings in one special section and adjust them individually: Virtual Technician (Kawai), Piano Designer (Roland), Piano Room (Yamaha Smart Pianist).
Most mid-range digital pianos already feature the key-off effect. Higher-priced digital pianos implement a more nuanced sound, which also takes the resonances of aliquot strings and duplex scale into account.
How the Key-Off Effect Works
Technically speaking, key-off samples are release samples, a technique developed in the samplers of the 80s and 90s. Its original purpose was to allow for a more realistic reproduction of the specific decay of acoustic instruments. Normally, playing a key triggers a sound; with key-off samples, the opposite is true: the MIDI function Note Off triggers the key-off samples. The intensity with which this happens is measured by the velocity at which the keys are released. The resulting value is called Release Velocity.
Smooth Release
On Yamaha digital pianos, you can find the term Smooth Release in addition to the key-off effect. This technique is essentially a part of the key-off effect that varies the key-off sound depending on how quickly you release the keys. On an acoustic piano, the decay phase is quite dynamic, depending on whether you play short notes staccato or portato, or release the note very gently. The velocity and duration of the note must also influence the key-off effect, otherwise we would perceive the decay of the notes as unnatural. Yamaha digital pianos with Smooth Release can simulate this sound behavior very authentically.