RIP Willie Mitchell one of my favorite soul producer/arranger/performers of all time.
"Groovin'" was the first track of his I found on 45 back when State Street Vinyl was still downtown. The opening 5 seconds were sampled for a Celph Titled track that featured Louis Logic, I think. Can't remember the name of the song off hand. I think it was around '02. Of course, the more famous sample comes about 6 seconds in, the loop that RZA sampled for GZA's "Liquid Swords". The intro to "Liquid Swords" was actually sampled from the intro of another Willie Mitchell track, which I think was on the b-side to a "Soul Serenade" 7-inch I have somewhere.