Born in New Haven, Connecticut, the son of a musical family, at age seven Frontiere was already playing several instruments before deciding to concentrate on the accordion.

[5] He composed several famous television themes of the 1960s, such as those for The Rat Patrol, Branded, The Flying Nun, and for producer Quinn Martin The Invaders, The Fugitive, and 12 O'Clock High.

He also composed the soundtrack to the 1971 motorcycle documentary On Any Sunday, which featured Steve McQueen and was directed by Bruce Brown.

Examples of Frontiere's sweeping, cinematic orchestrations appear in the opening and closing songs of the 1977 album Nether Lands by Dan Fogelberg.

[8] He was estimated to have scalped as many as 16,000 tickets, making a half million dollars in profit that he did not report to the Internal Revenue Service.