Bobby Hart, one half of the songwriting and production duo Boyce and Hart whose work helped define the sound of the 1960s television-made pop group the Monkees, died at his home in Los Angeles. He was 86.

Hart’s death was confirmed by his friend and co-author, Glenn Ballantyne, who said Hart had been in poor health after breaking his hip last year. Hart, born Robert Luke Harshman in Phoenix, Arizona, rose to prominence in the mid-1960s after teaming with Tommy Boyce to write and produce several of the Monkees’ best-known songs.

Boyce and Hart wrote the Monkees’ theme song and a string of hits including the No. 1 single “Last Train to Clarksville,” the top-five “Valleri,” and the rousing “I’m Not Your Steppin’ Stone.” Their work accounted for six tracks on the Monkees’ million-selling debut album; they also served as producers and used their backing band, the Candy Store Prophets, as session musicians. The team helped shape what Micky Dolenz later described as “the unique Monkee sound we all know and love” in a foreword to Hart’s 2015 memoir, Psychedelic Bubblegum.

As the Monkees gained cultural prominence through their television series and chart success, Boyce and Hart forged a parallel identity as performers and producers. They released albums together, appeared on television shows such as I Dream of Jeannie and Bewitched, and toured. Their songwriting range extended beyond upbeat pop: they penned the Monkees’ reflective “I Wanna Be Free,” and Hart co-wrote the daytime soap opera theme “Days of Our Lives.” Their songs were covered across genres, from Dean Martin to the Sex Pistols.

Hart’s career continued after the partnership with Boyce, who died in 1994. In the 1970s and 1980s he collaborated with other writers and artists, contributed material to the Partridge Family, and co-wrote “Over You” with Austin Roberts, an Oscar-nominated ballad performed by Betty Buckley in the film Tender Mercies. He also worked with Dick Eastman on material for the group New Edition.

The duo remained politically engaged during the late 1960s and early 1970s. They campaigned for Robert F. Kennedy during his 1968 presidential run and wrote the brassy “L.U.V. (Let Us Vote)” in support of the 26th Amendment, which lowered the voting age from 21 to 18 and was ratified in 1971.

Hart’s early life and development as a musician informed his later work. The son of a minister, he learned piano, guitar and the Hammond B-3 organ while in high school, and he operated an amateur radio station that grew into a small studio setup. After a stint in the Army reserves, he moved to Los Angeles in the late 1950s, intent on a career in radio and soon working as a session musician and songwriter. He toured as a member of Teddy Randazzo and the Dazzlers and co-wrote the song “Hurt So Bad,” a hit for Little Anthony and the Imperials that was later covered by Linda Ronstadt.

Boyce and Hart’s assignment to write for the Monkees came from Don Kirshner, who recruited the duo for Screen Gems’ songwriting operations when the television concept for the group was launched. Hart later recalled in his memoir how the theme song emerged from a simple street stroll, with Boyce strumming a guitar and Hart adding finger snaps and percussive vocal sounds that became part of the song’s signature opening.

The pair reunited with Monkees members for touring in later decades. Hart toured with Dolenz and the late Davy Jones in the 1970s, and the group Dolenz, Jones, Boyce & Hart released an album that helped sustain interest in the Monkees’ catalog. Renewed attention followed in the 1980s when the Monkees experienced a resurgence in popularity and in 2014 the duo were the subjects of the documentary The Guys Who Wrote ’Em.

Hart was married twice and is survived by his second wife, singer Mary Ann Hart, and two children from his first marriage. His collaborator Boyce also left a lasting imprint on popular music; he died in 1994.

Tommy Boyce, Davy Jones and Bobby Hart

Hart’s contributions to 1960s pop — as a songwriter, producer and performer — helped bridge television and the recording industry, producing songs that remained in circulation through covers, radio play and soundtrack use for decades. His memoir and the continued interest in the Monkees’ catalog have kept the work of Boyce and Hart in public view since their peak success more than half a century ago.