So Airplay is simply pushing music out to remote speakers, not actually controlling it?
Pretty much, airplay allows you to send your music to a variety of locations; other computers, apple TV’s, airplay enabled hifi’s etc.
The ‘remote app for iPod touch, iPhone and iPad is the easiest way to control what’s being played, if you have one of those devices then download the free app and get cracking it’s really pretty good.
As for the Sony being able to control playback, can’t really comment on that as it’s going to be a specific issue relating to the model of Sony.
What model is the Sony? With that detail it’s possible that someone could help.