In the '60s and '70s, much (if not most) contemporary improvisation was jazz-based. That began to change in the '80s, when a significant number of rock musicians began exploring the possibilities of free improvisation and new classical forms. Fred Frith is one of the more prominent. Co-founder of the underground British band Henry Cow in 1968, composer/improviser/guitarist Frith moved to the U.S. in the late '70s, where he began associations with such New York-based experimental musicians as cellist Tom Cora, harpist Zeena Parkins, saxophonist John Zorn, and percussionist Ikue Mori. Frith lived in New York for 14 years; some of his well-known ventures in that time included Massacre (with Bill Laswell and Fred Maher), Skeleton Crew (with Cora and Parkins), and his sextet Keep the Dog. In the '80s, Frith's compositional activities increased; he began writing for dance, film, and theater, and for such ensembles as the Rova Saxophone Quartet, Ensemble Moderne, Asko Ensemble, and his own Guitar Quartet. Primarily known as an improvising guitarist, Frith has also performed on bass (with Zorn's Naked City) and violin (with Lars Hollmer's Looping Home Orchestra). Frith has played on albums by the Residents, Brian Eno, Amy Denio, and René Lussier, to name just a few. Frith was the subject of Step Across the Border, a documentary film by Nicolas Humbert and Werner Penzels. By 2000, Frith was a professor of composition at Mills College in Oakland, CA.