Canadee-io - Nic Jones. It completely revolutionised my approach to the guitar and still is one of those songs that I can't listen to without going all gooey.

Dark Side of the Moon - Pink Floyd. It STILL sounds fresh and it's over thirty years old!

Anything played by Vin Garbutt on his whistle. He makes that instrument sing!

More will doubtless occur to me! I agree wholeheartly with Carol about Bach - without a shadow of a doubt the greatest musician who ever drew breath.