What would your ideal hold 'music' be?
I've always hated these things and think music is a terrible choice as it can only ever reinforce the 'middle of the road' tastes (something I have big problems with in NZ).
But the ringer sound just reduces your brain to mush after a few minutes as well...
Would silence work, with the occasional 'you're _n_th in the queue' update? I think that's my best choice