I'll have to second Liz The Squeak's choice of Mozart, for two readsons. For one, there would have been so much more great music composed by him if he lived longer, it staggers the mind to imagine it. Secondly, as Liz said, his music would have matured more. His late quartets show a hint of the advances he was starting to make, and he would have been a tremendous influence on further classical music development. I miss the Bothy Band. They're all alive and performing music, but that special mix when they were together is missed. As one who loves pipe music as well, Pipe Major G.S. McLennan was a great and prolific composer of highland pipe tunes, a child prodigy, and a pure genius. He died at age 45. There would have been a lot more great tunes entering the repertoire of Celtic musicians - not just of pipers - had he lived longer. I wish John Lennon would have been around for a real Beatles reunion. I wonder what other gems Woody Guthrie would have come up with.