If you have the app it should just play the music through that, we have a sonos system linked to the TV, computer etc and you install the app on your phone/ iPad /whatever and it just plays the music you have on that device. It doesn't download anything ( at least thats what I assumed- Im no expert though). I think its really excellent.
We have just bought a Sonos system and are having a few teething problems. Its loaded on to all our systems now and plays radio very well but not downloaded music from I pods- has anyone else come across this?