The thirty-ninth challenge is 'your favourite classical song'. I think this can be taken in any context so classical as in orchestral, as in classic rock - take it as you want to.
I've taken it as classical in the orchestral sense. My favourite classical song is 'The 5th' by David Garrett.
David Garrett is amazing. He plays violin instead of vocals for songs such as Smooth Criminal (Michael Jackson), Thunderstruck (ACDC), Kashmir (Led Zeppelin), Smells Like Teen Spirit (Nirvana), and Walk This Way (Aerosmith).