There are some tunes that rarely come along but can make you change direction.This tune "The Fubu Waltz" I heard at the "Ris Oranges" Folk Festival nr Paris many years ago at about 3 AM and I so loved it, as did other members of our band and not long afterwards we formed the group "Rosbif" and we started playing Traditional French Dance Music.
It was then played by two Hurdy Gurdy's, here it is played on a Jeffries Anglo Concertina.
http://www.youtube.com/watch?v=pvr1_ESdyZE

Are there any tunes that changed your musical direction?
Al