Mystery: no music shows up on Music app on my new iPod Touch

I've been using iOS devices for many years, plus I write iOS software, so even though I won't claim myself as an expert, I know enough about this whole iOS, iTunes and iCloud ecosystem so that I can focus on what is good and keep using it, while at the same time avoid the terrible aspects.

Among these, syncing music to iOS devices from iTunes is probably probably the worst, which is ironic since iPod is supposed to be the defecto music playback device.  The reality, though, is that because of those stupid DRM scheme here and there, putting music on an iOS device is always a multistep task, involving managing multiple iTunes libraries and all the crap along the way.

At the end, I am glad that there are ways to just leave music on the Cloud, and access them on demand.

Case in point: right now the "music" area of my iPod Touch generation 5 is like a untouchable  area.  No matter how hard to try using iTunes to sync, WiFi sync, open another library to sync, blah blah blah, no music can be sync to my iPod Touch.  I know it's not the cable problem because I can use it to deploy an iOS native app that I am writing.  I can also transfer photos and other crazy stuff.

So I am stuck in a sense that I can't use the music feature.  To a certain extend I should not care, because I already have my way to listen to music on the cloud.  Still it's annoying.