Looking back on Thrust which was released on this date in 1974 with some reflections on the recording process from drummer, Mike Clark:

“‘Actual Proof’ is a Buddhist term which signifies, through the act of chanting Nam Myoho Renge Kyo, that one can transform one’s inner life and the environment will respond in kind. I excused myself and sneaked into an empty studio and chanted twenty minutes. It was my determination that we make the first take undeniable, “actual proof,” for all the world to hear. Went back in and we did it. One take. It felt exactly as it sounds. And that’s why Herbie changed the name to “Actual Proof.”

The following day we did “Butterfly.” This tune has a very sensual mood and drips with wet colors, like a rain forest. Herbie really enjoyed writing and playing lush ballads like this. His playing here is simply beautiful. Bennie’s work here is provocative. His solos are soaked through with deep emotion and reveal his to be one of the most profound voices in jazz. Bill’s conga-slides at the start are a legendary part of the arrangement. Later Paul and I go into our thing with a double-time section.

That same day we recorded “Spank-A-Lee.” This was a tribute to the type of funk that was coming out of Oakland, California in the early seventies. Paul, Bill and came from Oakland, and since the three of us were on the ground floor, so to speak, of laying down this style, Herbie thought it would be fun to play one of these grooves. Herbie and Bennie are smokin’ all the way on this one. – Mike Clark, 1997