William “Poogie” Hart, lead singer and primary songwriter for Philly soul legends the Delfonics, has died. As TMZ reports, after experiencing trouble breathing, Hart was taken to Temple University Hospital in Philadelphia, where he later died due to complications during surgery. He was 77.

Growing up in Philadelphia, Hart sang in a number of vocal groups, usually with his brother Wilbert and other friends from Overbrook High School. In 1964, the Hart brothers formed the Orphonics with Randy Cain and Richie Daniels. Ricky Johnson was also in the group for a while, but the lineup soon solidified into the Harts plus Randy Cain. Upon linking with Thom Bell, a young producer who had worked with Chubby Checker, the trio rebranded as the Delfonics and began cranking out classics like “La-La (Means I Love You)” and “Didn’t I (Blow Your Mind This Time).” Typically, Poogie would write the songs, and Bell would produce and arrange them, adding the lush and emphatic string arrangements that came to typify Philly soul.

After a run of hits in the late ’60s and early ’70s, the Delfonics’ success waned a bit. Bell moved on to producing other acts. Cain left and was replaced by Major Harris. In 1975, the Delfonics split into two competing groups, each one featuring a different Hart brother. Membership in the groups fluctuated over the years, with some singers featuring in both versions of the group at times. The morphing and splintering continued for decades, but both Harts kept going. Even after Cain and Harris died in 2009 and 2012, the two versions of the Delfonics kept touring separately up until William’s death. The Hart brothers never reunited.

The Delfonics built up a staggering legacy for themselves. Beyond the greatness of the records in their own right, the group’s songs have been frequently covered, sampled, and synced. In 1996, William Hart’s version of the Delfonics featured on Ghostface Killah’s Ironman album. A year later, Quentin Tarantino made “La-La (Means I Love You)” and “Didn’t I (Blow Your Mind This Time)” key elements in his movie Jackie Brown.

Check out some Delfonics classics below.