A buuuuuunch of podcasts, mostly!
When thumbnailing and lettering, I listen to OSTs with no lyrics - the Child of Light OST has gotten me through a LOT of thumbnailing - but as soon as I'm at the inking/colouring stage of drawing, I switch over to the metric TON of podcasts I listen to.
Here's a handy list of what I currently fill my ears with:
(missing from that list is Rusty Quill Gaming and The Magnus Archives)
I prefer podcasts because they're usually 20 minutes or longer, which means that I focus for that long. With songs, you get 3-4 minutes, and then there's a tiny pause, and then another song, and another pause, etc. In that tiny pause between songs, my brain starts wandering.