[1] Their hit songs were primarily written by lead vocalist and founding member William "Poogie" Hart, and arranger and producer Thom Bell.

Their songs have been used in film soundtracks, including Quentin Tarantino's 1997 movie Jackie Brown, in which "La-La (Means I Love You)" and "Didn't I (Blow Your Mind This Time)" underscore the pivotal relationship between the characters played by Pam Grier and Robert Forster.

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

Members of some of these early groups included brothers William and Wilbert Hart, Ritchie Daniels, Randy Cain, and Jimmy Wroten, Stan Lathan, and Donald Cannon, friends who met at Overbrook High School in the 1960s.

A man named Stan Watson came into the barbershop one day, where William Hart, who had written quite a few songs by this point, would sing while playing his guitar.

Watson told William Hart that he knew a young arranger/producer for Cameo-Parkway Records named Thom Bell, who was at the time working with Chubby Checker.

William Hart recalls that the first song he presented to Bell was an original composition of his entitled "He Don't Really Love You".

[3] Bell immediately produced the music arrangement to that song and it was released on Moon Shot, which later became Cameo-Parkway Records.

[4] With Cameo-Parkway about to be defunct, Stan Watson started up his own label entitled Philly Groove Records and, in December 1967, "La-La (Means I Love You)" was first released to the local Philadelphia music market.

[6][4] The Delfonics and Bell had to work with a basic budget on the first creation as Thom explained "When I took them into the studio we didn't have any money to pay for string players and an orchestra so I played most of the instruments myself!

[7] "Didn't I (Blow Your Mind This Time)" also sold a million copies and by March 1970 received a gold disc from the R.I.A.A.

[4] However, in the absence of Bell, the Delfonics' career declined sharply, and with the exception of the aforementioned "Hey Love" and the minor hits "When You Get Right Down to It", "I Don't Want to Make You Wait" and "I Told You So", success eluded them after 1975.

While the main recording line-up of the group was William Hart, Major Harris, and Frank Washington, they would tour as two separate trios with additional members added.

One group featured William Hart, Randy Cain, and Garfield Fleming, and the other consisted of Frank Washington, Major Harris, and Freddy Ingleton.

The William Hart's with Major Harris and Frank Washington made several recordings, including backing vocals on the track "After the Smoke is Clear", on the 1996 hip hop album, Ironman by Ghostface Killah.

William Hart, along with Russell Thompkins Jr., the original lead singer of the Stylistics and Ted Mills the original lead singer of Blue Magic came together to record a CD entitled, The Three Tenors of Soul,[18] which was produced by songwriter and producer, Bobby Eli and released in 2007.