I jumped into the harmony pattern like i was born to it, and never left the track for a moment. It was like slipping into a suit made to order for you by a tailor, silk-lined all through. When two musicians hit it off like that right from the start, a fine glow of ease and contentment creeps over them. They’ve reached a perfect understanding through their music; they’re friends, seeing eye to eye. Maybe there’s a parable here for the world. Two guys, complete strangers, face each other, and while one takes off on the lead, the other feeds the accompaniment to him, helping him to render his solo and making the solo richer, spurring him on and encouraging him all the way. One feeds harmony while the other speaks his piece on the horn, telling the world what’s on his mind, supported every inch of the way by his pal. It’s like a congregation backing up the minister’s words with whispered “Amen’s” at the right places. The congregation never stands up and hollers “Shut up! You’re a liar!” while the minister’s preaching – that would be dischord, the whole spell of being together and united in a common feeling would be broken. That’s how it is when you play music with a man you understand and who understands you. You preach to him with your horn and he answers back with his “Amen,” never contradicting you. You speak the same language , back each other up. Your message and his message fit together like pie and ice cream. When that happens, man, you know you’ve got a friend. You get that good feeling. You’re really sent.
Really The Blues, by Mezz Mezzrow
-> here’s another quote from Mezz, about when rhythm sections went wrong