Bobby Hart, a songwriter best known for penning hits for the 1960s pop group the Monkees, has died at the age of 86. The news was shared by his friend and co-author Glenn Ballantyne, who said Hart’s health declined after he broke his hip last year.

Hart wrote the theme song for the Monkees’ television series, as well as the hits "Last Train to Clarksville" and "(I’m Not Your) Steppin’ Stone," which became staples of the band’s catalogue and of 1960s pop music more broadly.

The Monkees — Micky Dolenz, Davy Jones, Michael Nesmith and Peter Tork — were created for a television series that followed the misadventures of four young men who form a rock 'n' roll band. The show, which debuted in the mid-1960s, blended broad comedy with pop music and helped turn the group's recordings into chart successes.

Hart’s work with the Monkees provided some of the group’s most enduring songs, and his compositions helped define the sound that brought the television project commercial success. The songs he wrote for the group were widely played on radio and remain associated with the band’s era-defining profile.

Ballantyne, identified in reports as a friend and co-author, announced Hart’s passing and linked the decline in his health to complications after a hip fracture the previous year. No further details about the circumstances of Hart’s death or funeral arrangements were provided in the announcement.

Hart’s songwriting career intersected with the television and pop music industries at a moment when manufactured bands and cross-platform promotion were becoming prominent. The Monkees' combination of a weekly TV series and a recording career was among the period’s notable entertainment phenomena, elevating writers and producers behind the scenes as well as the performers on screen.

Tributes and further details about Hart’s life and legacy are expected to appear as colleagues, friends and representatives respond to the news. His songs with the Monkees continue to receive airplay and to be included in retrospectives of 1960s popular music.