Bobby Hart, the songwriter and producer who with partner Tommy Boyce helped create the Monkees' signature sound — penning hits such as "Last Train to Clarksville" and the show's theme song — has died. He was 86.

Hart died at his home in Los Angeles, according to his friend and co-author, Glenn Ballantyne. Ballantyne said Hart had been in poor health since breaking his hip last year.

Hart and Boyce were a prolific songwriting team during the mid-1960s, assembled by music supervisor Don Kirshner to supply songs for the Monkees, the made-for-television group modeled on the Beatles. Their compositions included the group's first No. 1 hit, "Last Train to Clarksville," and the memorable television theme whose opening lines, "Here we come, walkin' down the street," and chant, "Hey, hey, we're the Monkees," became part of the era's pop lexicon.

The Monkees' eponymous debut album sold more than a million copies and featured six songs by Boyce and Hart. The pair also worked as producers on the recordings and used their own backing band, the Candy Store Prophets, as session players. "I always credit them not only with writing many of our biggest hits, but, as producers, being instrumental in creating the unique Monkee sound we all know and love," Micky Dolenz wrote in a foreword to Hart's 2015 memoir, "Psychedelic Bubblegum."

As the Monkees pushed for greater creative control, Boyce and Hart pursued their own careers, releasing albums such as "Test Patterns" and "I Wonder What She's Doing Tonite" and making television appearances on programs including "I Dream of Jeannie" and "Bewitched." They also wrote other Monkees staples, including the wistful "I Wanna Be Free," and composed the theme to the daytime soap "Days of Our Lives."

Their songs crossed genres and generations, covered by artists ranging from Dean Martin to the Sex Pistols, whose version of "I'm Not Your Steppin' Stone" underscored the pair's broad influence. They also wrote "Valleri," a top-five single for the Monkees. Hart recounted in his memoir that the Monkees theme was born from a simple moment: Boyce strumming a guitar while Hart snapped his fingers and mimicked a hi-hat, then singing about walking down the street.

Beyond their work with the Monkees, Boyce and Hart were politically active, campaigning for Robert F. Kennedy during his 1968 presidential campaign. In 1971 the duo wrote the brassy "L.U.V. (Let Us Vote)" in support of the 26th Amendment, which lowered the voting age from 21 to 18.

Hart's songwriting career extended into film and television. In the 1970s and 1980s he managed hits with other collaborators and contributed material to the Partridge Family. He co-wrote "Over You," an Oscar-nominated ballad performed by Betty Buckley in the 1983 film "Tender Mercies," and worked with Dick Eastman on "My Secret (Didja Gitit Yet?)" for New Edition.

Boyce died in 1994. Hart later toured with former Monkees Dolenz and Davy Jones in the 1970s, and the trio released the album "Dolenz, Jones, Boyce & Hart." Renewed interest in the songwriters' work followed a Monkees comeback in the 1980s and the 2014 documentary "The Guys Who Wrote 'Em," which revisited their career.

Born Robert Luke Harshman in Phoenix, Arizona, Hart was the son of a minister. He taught himself piano, guitar and the Hammond B-3 organ, built an amateur radio station in high school, and after serving in the Army reserves moved to Los Angeles in the late 1950s to pursue a career in music. Early work included touring with Teddy Randazzo and the Dazzlers and co-writing "Hurt So Bad," a hit for Little Anthony and the Imperials later covered by Linda Ronstadt.

Hart was married twice and most recently to singer Mary Ann Hart. He had two children from his first marriage.

Hart and Boyce's body of work left a lasting imprint on 1960s pop and beyond, shaping the sound and success of one of television's most commercially successful music acts and producing songs that continued to be recorded and performed decades later.