Haha don't worry about it, here's how it works.
Your users cannot request a song to play on your iTunes playlist (namely because I'm not even sure if iTunes has a way to even do so without an Apple device). They can, however, see what song is currently being played by using the !song command. !requestsong only works with Youtube videos at this current point in time as does the inbuilt playlist on the music tab in Deepbot.
In this case only the !song command will work. I don't believe you can control the volume with the !volume command in this case. You would need to recreate your music library using Youtube videos if you want to give your users the ability to request songs. Lets be honest though, mostly everything music wise is probably on Youtube but on the flip side do you really want to give your viewers this kind of power? I'm sure you have your musical tastes and they will probably have theirs.
It's a lot of power to give them. Something to think about
Thanks,
Dante557