It wasn't until 1961 as the group became famous, they added bass, drums, and keyboards to the standard guitar backup and developed a funky sound that split the difference between gospel and rhythm and blues.
In a break with tradition, the groups sound incorporated Soul, R&B, and Rock; all of which flourishes in their musical mix (one of their early hits was produced by Gamble and Huff) without diluting the religious essence of their material.
The long-lived group flourished throughout the rest of the 20th century, scoring numerous Grammy Awards and nominations, as well as several hit albums along the way.
Based in Los Angeles, the original group members included Joe Ligon (d. 2016), Johnny Martin (d. 1987), Ermant Franklin Jr. (d. 1996), Artis Turnbough (d. 1999), Elmeo Franklin (d. 2008), Richard Wallace (d. 2020), Leon Polk (d. 1998), and David Walker (who also recorded several tracks with Link Wray under the name Bunker Hill).
[1] While reviewing the group's 1974 crossover LP It's Time, Robert Christgau wrote in Christgau's Record Guide: Rock Albums of the Seventies (1981), "You'd figure the showiest of all gospel groups would sell out with some flair, but the vocal transfigurations — that old Wilson Pickett (and Julius Cheeks) unhh born again — aren't the only reason this is one of the best LPs ever to come out of Philadelphia.