On Thursday, William "Poogie" Hart, co-founder and lead singer of pioneering soul group The Delfonics, died at 77-years-old.

R&B fans are mourning the passing of William "Poogie" Hart, co-founder and lead singer of Philadelphia soul group The Delfonics. On Thursday (July 14), Hart died at Temple University Hospital in Philadelphia after complications during surgery, according to TMZ.

During the 1960s and 70s, The Delfonics established themselves as a notable soul group, with hits including "La La (Means I Love You)," "Didn't I (Blow Your Mind This Time)," "Break Your Promise," "I'm Sorry," and "Ready or Not Here I Come (Can't Hide from Love)." The group was formed in 1965 by William, his brother Wilbert Hart and their schoolmate Randy Cain. With William serving as key songwriter for the group, The Delfonics signed to local imprint Cameo-Parkway Records releasing singles on MoonShot Records.

With production and arrangement from Philadelphia native Thom Bell, The Delfonics reached the mainstream after signing to Bell Records. Bell and William co-wrote 1968 Delfonics single "La La (Means I Love You)" which reached top five on the Billboard Pop and Soul charts. In 1971, the group won Grammy Award for "Didn't I (Blow Your Mind This Time)" in the Best R&B Performance By A Duo Or Group, Vocal Or Instrumental category. In 1975, The Delfonics split and William pursued a solo career as his brother, Wilbert, forming his own version of the group with new members as The Delfonics Review. The original lineup would never perform together again, as Randy Cain died in 2009.

Following their 1975 breakup, The Delfonics were repopularized in films including Jackie Brown, Crooklyn and The Family Man. Their songs “Ready or Not Here I Come (Can’t Hide from Love)” and “Funny Feeling” were also featured in Grand Theft Auto V on fictional radio station The Lowdown 91.1.