If you were playing the music so quietly that I could hardly hear it, and only for a few seconds as we passed, then I admit that it wouldn't bother me that much.
If you were riding in the same direction as me, at the same speed and playing loud tinny, distorted music like some people do on buses and trains with their phones then it would
really annoy me.
It also depends on where it was. If it was a busy road with lots of traffic, then it would already be noisy so a bit of extra noise wouldn't make that much difference.
Some of the areas I ride in are so peaceful that I can hear dogs yapping or cockerels crowing from about 2 miles away so any noise in a place like that would be really intrusive and unwelcome.
I'm not trying to get at you. I used to listen to a lot of music when I was younger, but to be honest, I don't think I've had wanted to do it when cycling. Music transports me to somewhere else, but when I'm cycling I'm already where I want to be. If I was doing a really boring commute, then perhaps some music would be nice, but I reckon I'd just concentrate on riding harder.
Anyway, no point in arguing when we could be out riding - if you do get a system for your bike, please don't turn it up too loud!