St-Onge studied double bass. Little is known of his formative years, but his first major musical activity was being recruited by Ambiances Magnétiques drummer Michel F. Côté to form the free improv trio Klaxon Gueule (also with Bernard Falaise). A first album, Bavards, came out in 1997, on which St-Onge performs in a classic American free jazz style. By the time the group's second CD, Muets, was released two years later, he had abandoned conventional playing, focusing on effects, electronics, and textures, dragging the formation into European-style electro-acoustic improv.
In the meantime, the bassist had met the other, mostly anglophone Montreal avant-garde scene, collaborating with the likes of Sam Shalabi (in his Shalabi Effect, with albums out on Alien8 Recordings), David Kristian (the trio Kristian Shalabi St-Onge, also on Alien8), and conceptual artist Christof Migone, once of the Quebec sound-art collective Avatar. St-Onge released a first solo album, Image/Négation, in early 1999. It established his fondness for the exploration of silence and noise, relating his work to artists like Francisco López, John Duncan, Bernhard Günter, and John Hudak.
On his second solo effort, Une Mâchoire et Deux Trous (1999, Namskeio), he built eerie textures by putting contact microphones in his mouth. This idea was developed into a performance-art concept with Migone in the duo Undo. The pair also founded the record label Squint Fucker Press in 2001. Meanwhile, St-Onge reached a certain level of success with the avant-psychedelic outfit Shalabi Effect. He also recorded an album with Godspeed You Black Emperor!'s Roger Tellier-Craig as Et Sans. ~ François Couture, Rovi