Music mostly for me and not music with words, just sound music. Usually something a bit upbeat or with a tempo to it to make me feel like I'm going at a decent pace and flow. Otherwise, if I'm home alone and the birds are singing, I just open the window and get going.
For me, in order to get in the zone, I have to enjoy what I do and not feel pressured into doing it. I have a whole system worked out as to how to schedule myself and work through things so I can get more "in the zone" moments and less acting like a dog getting distracted by every passing squirrel. My fiance also recently made me a fidget spinner thingy since we have a 3D printer, so whenever I need to think or get back into focus, I can play with that for a couple seconds and I feel my brain gets back into the task at hand.