This is a good question. According to an article written on the occasion of the release of "The Best Of The Love Unlimited Orchestra" CD (Funk Essentials series from the UK), Barry drummed himself in the late 60's for an artist called Jackie Lee while on tour.
With regards to his early releases, I think the answer might well be that it would have been some studio/session drummer. I have checked all my early BW/Love Unl/Love Unl Orch albums and none have credits other than for BW, his wife Glodean and Larry Nunes as spiritual advisor.
In the same article I referred to above, the way Barry worked was described as follows:
"He planned his orchestra work with care - nothing but professional players, full string complements of violins, violas and cellos, and totally live recordings with all the musicians crammed into the studio. No overdubs for the maestro."
What else can I say. He is indeed the one and only maestro!
