binarray2000 (binarray11111010000?)--
These are, as we say, "good problems to have."
Shifting mental gears is really a matter of practice and nothing more. And I think it's more a matter of shifting your perspective than anything else. We're often trying to change what we want in a given moment, when our desires are an outgrowth of our perspective. If we can shift our perspective -- which is much "lighter" than our desires, then the desires will shift as well and we can engage more fully in those other activities.
I've started experimenting with the idea of mental exercises (yoga) for this sort of thing. Literally working my mind through different states (postures) in short cycles (1 min). This seems to do two things. First, it strengthens the ability to make complete shifts and second, it will allow you to become more familiar with what those perspectives feel like so more can be aware of what state your in and shift if necessary.
So try this--Close your eyes and recall the feeling of being fully present ("in the zone") in your music; hold it for five slow, deep breaths. Then open your eyes and look to your right, focus on what's there for a deep breath then back to center. Close your eyes and recall the feeling of being fully present in writing code and hold it for five breaths. Open your eyes, look to the left, focus, and back to center. Repeat five or six times.
The idea behind looking to your right and your left is that changing your physical perspective will help change your internal perspective. If you're more kinesthetic than visual, try moving your body into a different position. Play around with it and see what works. Let me know your results.
Good luck!
Andy