The Uni-Vibe, also marketed as the Jax Vibra-Chorus,[1] is a footpedal-operated phaser or phase shifter for creating chorus and vibrato simulations for electric organ or guitar. Designed by audio engineer Fumio Mieda,[2] it was introduced in the 1960s by Japanese company Shin-ei (at the time Honey) originally branded as the Vibra-Chorus. The effect (now named Uni-Vibe) was modified to have easier access to its fuse, and a speed control foot pedal was added. It was later released in North America by Univox in 1968.[1][3]
It is commonly thought the Uni-Vibe is intended to emulate the "Doppler sound" of a Leslie speaker. However Fumio Mieda revealed in an interview the effect was based on hearing radio signals (like Radio Moscow) undergoing “atmospheric modulation”. The effect has made its mark on tracks like Robin Trower's "Bridge of Sighs", Jimi Hendrix's "Machine Gun" and Pink Floyd's "Breathe".[3]