from the great compilation from Mojo magazine, called 'the score' which profiles classic film soundtracks and composers. it has a myriad of songs from movies over the decades. spoilt for choice with this one to be honest and i had three posts lined up just from this but have pared it down to one so you can go find it and hear the rest.
taken from the soundtrack to 'don't play us cheap' by melvin van peebles this is a powerful track which is credited to Mrs. Washington & Co.who was actually a character in the movie (described at imdb as follows "A pair of devil-bats take human form and crash a Harlem house party in an attempt to break it up. But somehow, their attempts to ruin the party fail"). anyways, according to diddywah the singer is 'Joshie' Jo Armstead who played the character in the movie and musical and also co-wrote 'let's go get stoned' with ray charles. she also has a link to ruby andrews (who was recently sampled by the man himself q-tip).
so, for powerful, humbling, enlightenment go to it.