Many years back a friend (who is today a very accomplished guitarist/musician) had asked me to sing at a summer camp he went to. I think I was 20 and he was 15. I agreed to go and did. At the camp he asked if it would be OK to accompany me. I agreed but said, "No 13ths, 11ths, 9ths, 7ths, 6ths or flatted 3rds in this song. NONE, got it?" He said he did, wouldn't and didn't.

He and I played together on some songs recently, and he told me that story. He also said, "It was an easy promise to keep because I had NO idea what any of those things were."

FYI