A rather nice biography at allmusic.com:

Monte Dunn was one of a small group of guitar players who supplied musical accompaniment for Greenwich Village-based singer-songwriters of the 1960s. Although he never attained the heights of Danny Kalb, who went from backing up Phil Ochs and Judy Collins to leading influential folk-rock group, the Blues Project, and John Herald of the Greenbrier Boys, who recorded with Joan Baez, Dunn managed to play on some very influential recordings.

A sideman on Ian and Sylvia's albums, Northern Journey in 1964 and Early Morning Rain, a year later, Dunn gained further notoriety when the then-married Canadian folksingers attributed their version of the traditional folksong, "Nancy Whiskey", to him and folksinger Logan English. He went on to appear on Cher's album, All I really Want To Do in 1965, the debut self-titled album by Dylan pal, David Blue in 1966, Buffy Sainte-Marie's Fire & Fleet & Candlelight in 1967 and Peter, Paul and Mary's Late Again in 1968.

When a duo album, recorded with vocalist Karen Cruz, in 1969, failed to generate much sales, Dunn returned to studio work, subsequently appearing on albums by Tim Hardin, Richie Havens and Fred Neil.