EWI (from electronic wind instrument, pronounced EE-wee) is a type of wind controller, an electronic musical instrument. It was invented by Nyle Steiner, who conceptualized the idea in the 1960s, and developed the first working models in the 1970s.
The early models consisted of two parts: a wind controller and a digitally-controlled analog synthesizer in a rackmount box (which also houses the instrument's electronics). Japanese company Akai took over the instrument from Steiner and released several models (with his design help). The current top models, EWI4000S and EWI5000, contain a built-in digital synthesizer and don't require an external box. Akai also offers the EWI USB, a lower-priced model 4-octave that connects directly to a Mac or Windows computer and uses software for control.
EWIs use the Boehm fingering system used by most woodwind instruments, or they can be played with a simpler fingering system very similar to a recorder. The instrument feels somewhat like a soprano saxophone or clarinet, except that its keys are activated by touch rather than being depressed (i.e. the player's fingers don't rest on the keys).
Modern EWIs can be switched to flute, oboe, and saxophone fingering modes. The EWI4000s and EWI USB also have a special EVI (acronym for Electronic Valve Instrument) fingering mode that allows brass players to play the EWI. Like a straight soprano saxophone or clarinet, the EWI is straight with a slight inward bend a few inches below the mouthpiece, and it is held in front of the body with a neck strap. As of 2017, current models are the EWI4000s, EWI5000, and EWI USB.
The EWI has a silicone mouthpiece with sensors for air pressure (sending MIDI Breath Control by default) and bite pressure (which sends vibrato, more specifically a quick pitch up-down "blip" by default). Because the EWI keys do not move (instead, they sense when fingers are touching them by body capacitance, much like an elevator button works), the instrument is very agile. It also requires substantially less breath control than an acoustic instrument; breath sensitivity is one of the parameters that can be adjusted to the player's preference.
Unlike acoustic wind instruments, the fingering is identical in every octave. The current octave is determined by putting your left thumb between any two of the eight rollers. Touching a plate next to the rollers sends portamento by default. There are also pitchbend up and down plates, operated by the right thumb.
All EWI models can control external synthesizers or other MIDI instruments, either simultaneously or instead of the synthesizers that come with the instrument. Earlier EWIs require the external box unit, while the EWI4000S and EWI5000 have built-in MIDI outputs. The EWI USB has only a USB connector. Any EWI can play software synthesizers running on a computer. (All but the current EWIs require the computer to have a MIDI interface.)
Though it is often associated with jazz/rock fusion due to the analog synthesizers that came with the early models, the EWI is an extremely versatile instrument. The air pressure sensor allows for a considerable dynamic range.