After first becoming known as an experimental composer in New York City and Los Angeles in the early and mid-1960s, he became the leader of The United States of America, an innovative but short-lived band that integrated electronic sound and radical political ideas into rock music.

As a teenager, Byrd played accordion and vibraphone in a series of pop and country bands, started writing his own arrangements, and performed on some local TV shows.

[5] Byrd's 1962 Carnegie Hall recital was reviewed in prominent publications including The New York Times, which described the concert as a "thimbleful of tiny sounds" that were "generally just this side of the threshold of inaudibility.

The liner notes by Eric Smigel state:Crafted with technical precision, all of the works were designed to explore the "singularity of sound" that was central to Byrd's lessons with Feldman.

Byrd remains sensitive to the vertical qualities of any given pitch collection, but rather than presenting static drones or sequences of isolated chords, he frequently animates the relationship among the materials through indeterminate procedures and shifting cycles....

On one occasion in 1965, as the concluding part of a series of concerts and events called "Steamed Spring Vegetable Pie" (a title taken at random from The Alice B. Toklas Cookbook), Byrd organized a blues band fronted by his friend Linda Ronstadt, to play during a "happening".

With Barbara Haskell he co-produced the first West Coast festival of experimental arts,[2] before leaving UCLA in the summer of 1966 to create music full-time and produce "happenings."

[12] Recruiting bassist Rand Forbes, electric violinist Gordon Marron and drummer Craig Woodson (another member of the New Music Workshop), the band undertook their first live performances in late 1967, at the Ash Grove in Los Angeles.

[14] Electronic devices were used live as well as on the band's recordings, to process other instruments and Moskowitz's voice as well as providing their own musical textures, and the lyrics written by Byrd for some of the songs were markedly political.

For the relatively few who heard it, the record was a signpost to the future with its collision of rock and classical elements, although the material crackled with a tension that reflected the United States of America itself in the late '60s.

The album again made use of synthesizers and vocoder, along with an extended group of West Coast studio musicians including Tom Scott, guitarist Ted Greene, and uncredited bassist Harvey Newmark.

"[1] The extensive use of effects, delays, echoes, backwards vocals and other recording tricks and techniques are reminiscent of some of the experiments and work carried out by George Martin as well as Pink Floyd.

[15] Other album highlights include the equally psychedelic "The Elephant at the Door", and the politically charged "Invisible Man", written for and aimed at President Lyndon B. Johnson.

Two of the more unusual tracks on the record are "Mister Fourth of July"—a ragtime tune complete with scratchy 78 RPM-style effects—and "Leisure World", featuring narration from long-time ABC voice-over and "Ghoulardi" originator Ernie Anderson in an ode to California's first retirement mega-community.

Byrd estimated in 2002, in conjunction with a filing in the Napster music copyright case, that likely over 100,000 copies of The American Metaphysical Circus had been sold, yet he had never received a penny of royalties from Columbia/CBS/Sony.

[15] While working with the United States of America in 1967, Byrd provided an arrangement and electronic music for "Crucifixion" on Phil Ochs' album Pleasures of the Harbor.

"[21] He scored a number of films, including Agnès Varda's 1969 Lions Love, Bruce Clark's 1971 The Ski Bum with Charlotte Rampling and Zalman King, The Ghost Dance (1980) and Robert Altman's ill-fated H.E.A.L.T.H., which was originally shot in 1979, but had its U.S. release delayed until 1982 because of a shakeup in the management of 20th Century Fox.

For White Elephant, a collaboration between these three parties, he created a graphic score as "a kind of 'space opera' - in the form of an imaginary space mission outside our galaxy in the year 9050.

Photographs from NASA's Hubble Space Telescope are the basis for the score, consisting of a mixture of listed, sampled and improvised sounds in parallel to an electronic soundtrack created by Dreams of Tall Buildings."