A wind controller, sometimes referred to as a wind synthesizer, is an electronic wind instrument. It is usually a MIDI controller associated with one or more music synthesizers. Wind controllers are most commonly played and fingered like a woodwind instrument, usually the saxophone, with the next most common being brass fingering, particularly the trumpet. Models have been produced that play and finger like other acoustic instruments such as the recorder or the tin whistle. The most common form of wind controller uses electronic sensors to convert fingering, breath pressure, bite pressure, finger pressure, and other gesture or action information into control signals that affect musical sounds. The control signals or MIDI messages generated by the wind controller are used to control internal or external devices such as analog synthesizers or MIDI-compatible synthesizers, synth modules, softsynths, sequencers, or even non-instruments such as lighting systems.

Simpler breath controllers are also available. Unlike wind controllers, they do not trigger notes and are intended for use in conjunction with a keyboard or synthesizer. A breath controller can be used with a keyboard MIDI controller to add articulation and expression to notes sounded on the keyboard. For example, a performer who has pressed a long held note on the keyboard with a sustained sound, such as a string pad, could blow harder into the breath controller set to control volume to make this note crescendo, or gradually blow more and more gently, to make the volume die away.

Some wind controllers contain a built in sound generator and can be connected directly to an amplifier or a set of headphones. Some even include small built in speakers such as the Roland Aerophone series and the Akai EWI SOLO, however their small speaker systems cannot reproduce bass notes correctly or provide adequate sound levels for serious live performance, so these built in sound systems are strictly for home practice at modest playback levels. Some wind controllers such as EWI USB, Berglund NuEVI and NuRAD are strictly "controllers" and do not make a sound on their own, and thus must be connected via MIDI or USB to a sound generating device (or a soft synth). For this reason, a wind controller can sound like almost anything (depending on the capabilities of its sound generator). Wind controller models such as the Akai EWI5000, EWI SOLO, and Roland Aerophones have built-in onboard sample sounds, as well as the MIDI and/or USB outputs. The now discontinued EWI 4000s had a DSP subtractive synthesizer built in rather than sampled instruments and so remains popular on the second hand market.

The fingering and shape of the wind controller put no acoustic limitations on how the wind controller actually sounds. For example, a wind controller can be made to sound like a trumpet, saxophone, violin, piano, pipe organ, choir, synthesizers or even a barnyard rooster. Whether designed primarily to appeal to woodwind, brass or harmonica players, controllers can produce any virtual instrument sound. Some virtual instruments and hardware synthesizers are better suited to adaption for wind controller performance than others. A hardware or software synthesizer's suitability is largely dependent on the control options available. MIDI CC mapping options allow the player to control elements like the filter cut off via breath control for expressive dynamics. Custom patches (or presets) are required for optimal expressivity, to take advantage of the considerable benefits of wind control.