电钢琴是一种电气乐器，外形和钢琴类似。与使用合成器的电子钢琴的不同在于它使用机械发声，再经由拾音器转化成电信号，发声原理和电结他类似，都是以模拟信号直接输出到电钢琴专用的乐器放大器或输出到录音设备，而非像钢琴般以其木箱外壳来直接共鸣发声。

和钢琴类似的地方是，其木造琴键牵动钢琴内部包着绒毡的小木槌，这结构是一模一样的；继而敲击钢丝弦发出振动，这个运作原理都是相同的。不同的地方是，并不是以箱体的的振动发声，而是运用了电磁学原理，由每条琴弦对应的每粒拾音器来感应并收集每条琴弦的振动。当琴弦振动时，切割了拾音器的磁感线，从而使拾音器接上的导线中产生不同频率的电流，当这些电流通过电辅音箱还原时，就成了电钢琴的声音。

An electric piano is an electric musical instrument which produces sounds when a performer presses the keys of the piano-style musical keyboard. Pressing keys causes mechanical hammers to strike metal strings, metal reeds or wire tines, leading to vibrations which are converted into electrical signals by magnetic pickups, which are then connected to an instrument amplifier and loudspeaker to make a sound loud enough for the performer and audience to hear. Unlike a synthesizer, the electric piano is not an electronic instrument. Instead, it is an electro-mechanical instrument. Some early electric pianos used lengths of wire to produce the tone, like a traditional piano. Smaller electric pianos used short slivers of steel to produce the tone. The earliest electric pianos were invented in the late 1920s; the 1929 Neo-Bechstein electric grand piano was among the first. Probably the earliest stringless model was Lloyd Loar's Vivi-Tone Clavier. A few other noteworthy producers of electric pianos include Baldwin Piano and Organ Company and the Wurlitzer Company.