Definition of an Electric Piano.

An electric (electro-mechanical) piano is a touch sensitive keyboard instrument, in which the tone sources are struck or plucked mechanical resonators. In principle it thus resembles an acoustic piano, but a sound board is usually dispensed with. Electrical transducers are used to pick up resonator vibrations, the output being amplified and/or directly recorded.

For completeness, electro-mechanical clavichords & harpsichords are also included.

In theory it may be possible to build a piano using purely electrical means of sound signal generation. With no mechanical resonators or electronics. No practical instrument of this type has yet been devised (see Telharmonium).

There are a variety of ways in which electronic piano synthesis can be accomplished. Early types were analogue, mostly subtractive: Individual oscillators, as in the RMI piano or a divided master oscillator in most other efforts. Early digital designs include the Yamaha PF series, using FM synthesis, a more interesting sound than subtractive analogue.

Most current electronic pianos produce sound by playing short recordings (samples), of genuine acoustic or electro-mechanical instruments. These are usually more realistic than analogue types & are getting better. They currently still fall short of the performance capabilities & feel of the originals that they imitate.