iPhone Music / iTunes syncing glitch

Over the past few months I've been puzzled by this issue.

Here's a screen shot of my iPhone's music library, displayed in iTunes. As you can see, according to iTunes, there is no music on my phone.



But...in my iPhone music app, there is a ton of music (all of which I thought I had deleted--so did iTunes, I suppose). This music still all plays, also, when selected.



Any ideas? Syncing has become a huge mess... and I'm not sure why.

Newest version of iTunes installed, iOS6 on a 4S.

Thanks for any insight or help.