The violinist Erich Friedman is, I believe, a dentist.  Also Alan
Rawsthorne trained as a dentist.  Alban Berg started in the Civil Service.
Borodin practised medicine as well as being a research chemist.  Havergal
Brian started as an organist, was an apprentice joiner for a time, played
the violin and cello and later became a music journalist.

Tim Horwood