Do you know Singers Unlimited? They're an incredible vocal group from the 70s founded by Gene Puerling. He's a genius vocal arranger and singer, first got a little traction in the Hi-Lo's. Don Shelton was also in the Hi-Lo's and he and Puerling worked with Bonnie Herman and Len Dresslar in the Chicago commercial music scene, recording jingles and the like day in day out. Dresslar is best known as the man who sings, "Ho ho ho" in the Jolly Green Giant commercials.
The four of them formed Singers Unlimited and Puerling wrote some out there vocal arrangements with them split into many, many parts. I think their a cappella "Fool On the Hill" splits into fifteen parts at the end. Their first album was with the Oscar Peterson Trio, and the first track on that album was the theme from *Sesame Street!* I think they must have been the whitest people to ever sing with the Oscar Peterson Trio.