I've often thought that musicians and composers seem to stick with the more formal versions of their first names but I'm sure that there are some counter-examples. Mike Tippett? Benny Britten?
Britten was known as Ben to everyone who knew him - not in concert programmes though. I was rather shocked when I discovered that the name Benjamin (a lovely name, I think) was abbreviated. Auden called him "Benjy".
First names in my school, but then we were girls, who for some reason were always treated much better than boys were.