Founded in 2005 by instrument designer Keith McMillen in Berkeley, California, Keith McMillen Instruments (KMI) specializes in expressive MIDI controllers built around a proprietary smart sensor fabric — a variably resistive felted material embedded with carbon nanoparticles that eliminates moving parts while capturing nuanced gestures like pressure, velocity, and tilt. The company grew out of McMillen's decades of experience in music technology, including his earlier venture Zeta Music, which pioneered electronic string instruments before being acquired by Gibson in 1992.

KMI's product line spans keyboards, pad controllers, foot controllers, and a digital mixer. The QuNexus and K-Board Pro 4 are MPE-capable keyboard controllers that transmit per-key pressure and position data. The QuNeo is a multi-touch pad controller popular with electronic producers and DJs, while the BopPad serves as an expressive drum pad. The SoftStep3 and 12 Step2 are MIDI foot controllers designed for hands-free live performance control, and the K-Mix combines a programmable digital mixer, audio interface, and MIDI control surface in a compact format.

The company's controllers have been adopted by a wide range of artists, including Jordan Rudess of Dream Theater, John Paul Jones of Led Zeppelin, Adrian Belew of King Crimson, Vernon Reid of Living Colour, Richie Hawtin, and many others across genres from progressive rock to electronic music.

Keith McMillen Instruments has 22 products cataloged on Equipboard, including MIDI Foot Controllers, MIDI Keyboard Controllers, and MIDI Interfaces. Their gear is featured by 63 artists, with the strongest followings in Electronic, Rock, and Pop. Notable users include Doug Wimbish, Trey Gunn, and Vernon Reid. Keith McMillen Instruments's catalog spans the full price spectrum — from entry-level options to high-end flagships.