How do I contact iTunes S.a.r.l. About a glitch in the remote app?

There has been an ongoing glitch with the remote app that still hasn't been fixed. When listening to music on multiple speakers and using the remote to turn off the computer speakers the volume on the remote ones goes straight to maximum. It doesn't happen if there is more than three sets of speakers running, only if the computer ones and one remote set, ( or so it would seem)

It is definitely an app issue as I have a mac running iTunes and the computer speakers and two airport expresses running monitor speakers and a full hifi system.

Anyhow, how do I contact the app developer to let them know?

Thanks