Dan Gooch mentioned to me on the CSN list about 5 years back that while he was working at Motown in the 1960's that he and the other engineers would prepare a special backing track for the Sullivan show. In the case of the Supremes...The instruments and Flo and Mary's voices would usually be canned, while only Diana's lead was live. It should be noted too that there were exceptions to the no lip-synching on the Sullivan Show. The Mamas and the Papas lip synched their first appearance completely (it would be impossible to recreate that sound live...that was a studio sound if there ever was one!). You can *barely* hear them singing along with and doubling the pre-recorded track in places.