Argentine clarinetist and alto saxophonist Guillermo Gregorio was born on May 1, 1941, in Buenos Aires. Influenced early on by jazz musicians such as Pee Wee Russell and Jimmy Noone, he later explored the work of Lennie Tristano, Ornette Coleman, and early musique concrète. In the early 1960s, Gregorio began experimenting with avant-garde music, culminating in the project "Unheard Music," later released in the album Otra Música: Tape Music, Fluxus, and the Improvisation in Buenos Aires 1963–1970. In the mid-1980s, he moved to Europe, living in Vienna and collaborating with Franz Koglmann, before eventually settling in Chicago. There, he founded the Madi Ensemble in 2001, further developing Argentine avant-garde styles. Gregorio has collaborated with numerous contemporary musicians and released several albums, including Ellipsis (1997) and Background Music (1998).