The greatest outfit in soul music history. At Wattstax.
He's mostly remembered for "Shaft" and, in this generation, for starring as Chef on "South Park," but as Oliver Wang argues on the essential Soul Sides
mp3 blog, his contributions to Stax/Volt as a singer/songwriter were almost without parallel.
Remember that before Hayes ever graced his own album covers, he and writing/composing partner David Porter had penned some 200 songs for Stax/Volt Records; theirs was one of the most prolific and important of collaborations. The Hayes/Porter name, like Motown's Holland-Dozier-Holland or Philly Intl's Gamble-Huff, was like a stamp of excellence for most of the singles and albums the credit appeared on. They are best known for Sam and Dave's hits like "Soul Man" and "Hold On, I'm Comin" but my personal favorites were some of the tracks they wrote for Stax/Volt's female artists...
Wang's got 10 tracks Hayes either wrote or performed, including the Charmels "As Long as I've Got You," which is one of the greatest obscure singles in all of soul.
Do yourself a favor, buy the complete singles
Also, check Hayes' influence on hip-hop