William Hart, lead singer of music group The Delfonics, dies at 77

William "Poogie" Hart, lead singer of Grammy-winning R&B group The Delfonics, has died, TMZ has learned.

His son, Hadi, tells TMZ...William was having trouble breathing, so he was recently taken to Temple University Hospital in Philadelphia, where he died Thursday following surgery.

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William and his brother, Wilbert, started the Philadelphia-based band in the late '60s with Randy Cain, Ritchie Daniels and Thom Bell. The band would have a major impact on the development of the Philadelphia sound, known as T.S.O.P.

William and Thom exclusively wrote all the songs, including hits such as "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)".

In 1971, The Delfonics won a Grammy Award for "Didn't I (Blow Your Mind This Time)" for Best R&B Performance by a Duo or Group, Vocal or Instrumental.

“Didn’t I” and “La-La” were also featured in Quentin Tarantino’s movie “Jackie Brown.” Other films that have popularized their music are Spike Lee's "Crooklyn" and "The Family Man" starring Nicolas Cage.

Their songs "Ready or Not Here I Come (Can't Hide from Love)" and "Funny Feeling" were played in the video game "Grand Theft Auto V" on a fictional radio station The Lowdown 91.1.< /p >