Since I read the book Jim Henson's Designs and Doodles, I always thought Don Music debuted in 1981, because the caption under the sketch of the character said 1981. But if you read the final "Dear Sez Me" section (the fan mail section) in the book Sesame Street Unpaved, you'll see that some people ages 25-30 wrote in and said they recalled a character who would hit his head against the piano, and asked what his name was? I'm thinking, if they were around 30 years old in the mid '90's (when the book was written), then that means they may have watched SS in the mid '70's.