In the beginning we knew whether something we played was good or not. Even though we were trying out new things, our approach was still pretty much tied in with a more traditional way of playing. But the more the stuff developed, the harder it became to tell if what we were doing was working or not. For one thing, Miles more and more recorded things in bits and pieces, just little ideas here and there that were later on strung together. It was fascinating to work like that, but during the recording sessions we couldn't tell if the stuff was good or bad, or what it was at all. We'd play and then we'd wonder, "What was that? What did we do?"'

Herbie Hancock, on working with Miles Davis in the late '60s.