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A stage piano is an electronic musical instrument designed for use in live performance on a stage or a studio, as well as for low-budget music recording. While stage pianos share some of the same features as digital pianos designed for home use and synthesizers, they have a number of features which set them apart. Stage pianos usually provide a smaller number of sounds (acoustic piano, electric piano, and Hammond organ), unlike regular digital pianos and synthesizers.
Controls and features
Stage pianos usually have a smaller selection of sounds than digital electronic keyboards and synthesizers. Instead of the hundreds of sounds and complex oscillator controls available on a high-end, professional synthesizer, they often have a small number of sounds, typically a variety of acoustic piano, electric piano, and Hammond organ sounds. Also, instead of scrolling through the on-screen menus used on synthesizers, stage pianos are usually controlled with simple knobs and buttons.
Stage pianos differ from inexpensive home digital keyboards in a number of ways. Home digital keyboards provide several hundred sounds, ranging from imitation electric piano and flute sounds to buzzy synth-style sounds. However, the imitation sounds are created by relatively simple synthesis methods, rather than by sampling or complex Digital Signal Processing-modelling, as in the case of a high-end stage piano. This means that the sound quality of presets are not suitable for a professional performance.
Stage pianos often have a heavier, more robust body, which is better able to withstand the stress of heavy touring. Unlike digital pianos designed for home use, they do not have a fixed stand or fixed sustain pedals. Instead, they are designed to be used with a separate portable stand and portable, plug-in sustain pedals. This makes stage pianos easier to transport on tours.
While almost all digital pianos and lower-end synthesizer keyboards designed for home use have small onboard powered speakers, stage pianos are often designed without onboard speakers; instead, they are designed to be used with external amplification. While small, low-powered amplified speakers may be appropriate for in-home use, they cannot provide sufficient power for on-stage monitoring in rock and jazz performance settings. While most onboard powered speakers produce between 6 and 40 watts per speaker, a typical professional keyboard amplifier will produce over 300 watts. Nevertheless, some stage pianos, such as the Yamaha P-250 or Casio Privia, do have onboard powered speakers.
Most stage pianos provide a recreation of the electro-mechanical electric pianos that were based on picking up the sound of a metal tine, reed or string hit by a hammer, such as the Fender Rhodes, Wurlitzer 200A or Yamaha CP-70/CP-80 series. Instead of using tines or strings, stage pianos reproduce sound electronically by the use of sampled or digitally modelled sounds. They usually have MIDI interfaces to permit them to be used as master keyboards, which can control other tone-generating modules, such as Hammond organ-emulators or synthesizer string modules.
Most digital stage pianos have weighted keys or semi-weighted keys. The difference is how much force it will take you to push on the keys and how much the keys feel like those of an acoustic piano.
- Fully weighted keys are designed to replicate the weight and playing action of acoustic piano hammer-action keys - they give a more piano-like feel and better touch control. This type of keys are more expensive than semi-weighted keys and make the instrument heavier to lift.
- Semi-weighted keys save weight, which is an important consideration for a mobile stage piano that will be taken on tour. They give less control, but can be played faster by most people.
Stage pianos usually have 88 keys, which is standard for all modern acoustic pianos. However, some stage pianos have fewer keys, such as the Kurzweil SP76. It has only 76 semi-weighted keys, but is still called a stage piano because of its layout and weighted keys.
While the sounds or "voices" available on stage pianos is often wider than that of a digital piano designed for home use, stage pianos have far fewer voices than a typical electronic synthesizer. Stage pianos usually have a smaller selection of voices, typically acoustic piano, electric piano, Hammond organ, and a few others. Some stage pianos also provide a few basic synthesizer functions, to enable performers to play accompaniment "pads" or synth "leads."
Common stage pianos
- Casio Privia line: Contains high-quality instrument sampled data, such as four-layer samples (more expression of tone for varying velocities) for the pianos. They have 88 weighted keys, tuning control, and 128-voice polyphony, amongst other features. The Privia family is equipped with 16-watt onboard speakers in almost all models, except for PX-3 and PX-5S models. Earlier Privia models use Zygotech synthesis engine, while newer models utilizes Casio's new Linear Morphing Technology.
- Nord Stage line: Produces organ, piano and synthesizer sounds. Available in 76 or 88 weighted-key models, as well as a semi-weighted model for reduced weight.
- Clavia Nord Electro 3: Sold in 61 or 73-key semi-weighted action models. Produces organ and piano sounds, but also other sounds from the Nord Piano Library and Nord Sample Library.
- Korg SP-series: Features 88 fully weighted keys with RH3 (Responsive Hammer 3) action with 3x10 tone banks. It also has a pair of 11-watt built-in speakers suitable for relatively small performance venues.
- Kurzweil SP88X: Has 76 and 88-key semi-weighted action models, and an 88-key fully weighted action model. Its sounds include pianos, various Hammond-organ sounds, and synthesizer string sounds.
- Kurzweil SP3X: Contains 512 preset sounds, 128 effects, 60 rhythm patterns and weighted keyboard action that is velocity and aftertouch-sensitive. It has 88 keys and 64-note polyphony 
- Roland RD series (RD-150, RD-300SX, RD-700 etc.): The keyboard has a full-weighted 88-key keyboard with graded hammer action. It uses high quality acoustic, electric and Rhodes piano samples, additionally providing other lead and backing instruments (e.g. clavinet, electric and acoustic bass, string/synth pads and vocal effects). It is designed for live use, and the operation panel includes the most used functions to avoid on-screen menus.
- Yamaha P-250 and CP300: Digital stage piano designed for professional live performance or for use as a studio instrument. Includes stereo grand piano samples, 88-key Graded Hammer (GH) action, MIDI-controller capability, and on-board speakers.
- Yamaha CP33: This series of stage piano was first introduced in 1976. It has an 88-key Graded Hammer keyboard action, 28 voices, and MIDI master keyboard controller capability.
- M-Audio ProKeys 88: Has 88 hammer-action keys, a stereo grand piano sound, 14 other instrument sounds, and MIDI controller functionality.
- Korg SP250: Features 88 fully weighted keys, MIDI controller functionality and a total of 30 piano, organ, string and pad sounds. Designed for touring, it is barely more than twice the size of the keyboard itself.
- Yamaha CP4 Stage: The latest version of Yamaha's CP line of professional stage pianos. Includes revamped stereo piano samples, 88-key Graded Hammer (GH) action, MIDI-controller capability, and new sound engine based on the home-focused Clavinova digital pianos.
- Kawai MP7: Kawai's first model of stage piano. Also features 88 weighted keys with steteo piano samples powered by Harmonic Imaging Technology.
-  Kurzweil Music Systems product page for the SP3X