A. I use Spotify sparingly. They have a bug that's been around for awhile. Their ads automatically minimize whatever program you have focus on, and shifts that focus to Spotify. While gaming, this can be fatal.
B. Rarely do I listen to music on Youtube, even though I have a couple lengthy playlists. I will usually have other things playing. Entire seasons of Yu-gi-oh Abridged and Dragon Ball Z Abridged, or seasons of MLP. Because I'm so familiar with them, I can listen to them, just for background noise (and in some cases I've noticed things I never have before). Stand up comedy, anything really. The one playlist I do listen to, it's music I can't get on Spotify (though when they allow user-uploaded music, and fix that stupid bug, it's gonna be a good day.)
Diablo 3 is the only non-Steam game I play, and Torchlight 2 offers Windowed Full Screen. I have not had an issue with it yet. I will check some stuff out later, to see if the issue continues, or if it exists with Torchlight 2. But for now, Monday Night Football.