An electric piano is an electric musical instrument.
Electric pianos produce sounds mechanically and the sounds are turned into electronic signals by pickups. Unlike a synthesizer, the electric piano is not an electronic instrument, but electro-mechanical. 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.
The popularity of the electric piano began to grow in the late 1950s, reaching its height during the 1970s, after which they were eventually replaced by synthesizers capable of piano-like sounds without the disadvantages of moving mechanical parts. Many models were designed for home or school use, or to replace a heavy and un-amplified piano on stage, while others were conceived for use in school or college piano labs for the simultaneous tuition of several students using headphones.
Due to their size and weight, digital stage pianos have replaced many of the original electromechanical instruments in contemporary usage. However, In 2009, Rhodes Music Corporation started producing a new line of electro-mechanical pianos, known as the Rhodes Mark 7.
The actual method of tone production varies from one model to another:
Yamaha, Baldwin, Helpinstill and Kawai's electric pianos are actual grand or upright pianos with strings and hammers. The Helpinstill models have a traditional soundboard; the others have none, and are more akin to a solid-body electric guitar. On Yamaha, Baldwin and Kawai's pianos, the vibration of the strings is converted to an electrical signal by piezoelectric pickups under the bridge. Helpinstill's instruments use a set of electromagnetic pickups attached to the instrument's frame. All these instruments have a tonal character similar to that of an acoustic piano.
Wurlitzer electric pianos use flat steel reeds struck by felt hammers. The reeds fit within a comb-like metal plate, and the reeds and plate together form an electrostatic or capacitive pickup system, using a DC voltage of 170v. This system produces a very distinctive tone – sweet and vibraphone-like when played gently, and developing a hollow resonance as the keys are played harder. The reeds are tuned by adding or removing mass from a lump of solder at the free end of the reed. Replacement reeds are furnished with a slight excess of solder, and thus tuned "flat"; the user is required – by repeated trial and error – to gradually file off the excess solder until the correct tuning is achieved. The "Columbia Elepian," also branded as "Maestro" uses a reed system similar to the Wurlitzer.
The tuning-fork here refers to the struck element having two vibrating parts – physically it bears little resemblance to a traditional type. In Fender Rhodes instruments, the struck portion of the "fork" is a tine of stiff steel wire. The other part of the fork, parallel and adjacent to the tine, is the tonebar, a sturdy steel bar which acts as a resonator and adds sustain to the sound. The tine is fitted with a spring which can be moved along its length to allow the pitch to be varied for fine-tuning. The tine is struck by the small neoprene (originally felt) tip of a hammer activated by a greatly simplified piano action (each key has only three moving parts including the damper). Each tine has an electromagnetic pickup placed just beyond its tip (see also tonewheel). The Rhodes piano has a distinctive bell-like tone, fuller than the Wurlitzer, with longer sustain and with a "growl" when played hard. Hohner's "Electra-Piano" uses a similar system, with a metal reed replacing the Rhodes' tine. Its sound is correspondingly somewhere between the Rhodes and Wurlitzer.
Hohner's original Pianet uses adhesive pads made from foam rubber and leather impregnated with a viscous silicone oil to pluck metal reeds. When the key is released, the pad acts as a damper. An electrostatic pickup system similar to Wurlitzer's is used. The tone produced resembles that of the Wurlitzer but brighter and with less sustain. The same firm's "Cembalet" uses rubber plectra and separate dampers but is otherwise almost identical. Hohner's later "Pianet T" uses silicone rubber suction pads rather than adhesive pads and replaces the electrostatic system with passive electromagnetic pickups similar to those of the Rhodes, the reeds themselves however being magnetized. The Pianet T has a far mellower sound not unlike that of the Rhodes instruments. None of the above instruments have the facility for a sustain pedal.
A close copy of the Cembalet is the "Weltmeister Claviset," also marketed as the "Selmer Pianotron." This has electromagnetic pickups with a battery-powered preamplifier, and later models have multiple tone filters and a sustain pedal.
Although not technically pianos, the following are electric harpsichords and clavichords.
Baldwin's "Solid-Body Electric Harpsichord" or "Combo Harpsichord" is an aluminum-framed instrument of fairly traditional form, with no soundboard and with two sets of electromagnetic pickups, one near the plectra and the other at the strings' mid-point. The instrument's sound has something of the character of an electric guitar, and has occasionally been used to stand in for one in modern chamber music. Roger Penney of Bermuda Triangle Band worked on the design and development of the original instrument for the Cannon Guild Company, a premier harpsichord maker located in Cambridge Massachusetts. This instrument had an aluminum bar frame, a spruce wood soundboard, bar magnetic pickups, and a Plexiglas (clear plastic) openable lid. The prototypes and design were sold to Baldwin who made some modifications, and then manufactured the instrument under their own name.
Hohner's "Clavinet" is essentially an electric clavichord. A rubber pad under each key presses the string onto a metal anvil, causing the "fretted" portion of the string to vibrate. When the key is released, the whole string is theoretically free to vibrate but is immediately damped by yarn woven across the far end. Two electromagnetic single-coil pickups under the strings detect the vibrations which are then preamplified and filtered.
As with electric vs. acoustic guitars, the sound of most electric pianos differs considerably from that of an acoustic instrument, and the electric piano has thus acquired a musical identity of its own, far beyond that of simply being a portable, amplified piano. In particular, the Rhodes piano lends itself to long, sustained "floating" chords in a way which would be impossible on an acoustic instrument, while the Hohner Clavinet has an instantly recognizable vocabulary of percussive riffs and figures which owe less to conventional keyboard styles than to funk rhythm guitar and slap bass. Early Wurlitzer models had vacuum tube amplifiers, which could be over-driven to create a distinctive distortion. Later transistorized models, while sharing a similar mechanical approach to sound generation, didn't replicate the "fat" sound of the tube-based models, but instead sported a soulful and useful tremolo.