Can anyone think of the name of this book?

It’s a story about a young boy who wants to learn how to play a guitar and the old man who teaches him. There’s also a little dog who belongs to the man and pops up throughout the book.

It doesn’t begin in the U.S., but ends up here? The old man plays magnificently. The story is told by other people relating their experience with this boy who has grown up to become an amazing musician. It’s a true story, because it mentions famous people who heard the boy play after (or as) he grew up.