A couple years ago, Stanford hosted an evening with Leonard Cohen and Philip Glass. Over an hour of conversation (pdf transcript), AND they made the audience submit questions via notecards! A good bit from Glass:

Someone recently was showing me a book that this person was writing and she said, do you have any advice? I said, Yes, my advice is: Don’t stop working before the book is finished. And I quickly added: Because it’s in the last moments of the work that the quality appears. It doesn’t happen at the beginning; it happens at the end.