Seems to me you might want to check in with your Dr.
Hypothyroid(low thyroid) can cause cold extremities. There are other medical conditions that might cause the cold as well e.g. poor circulation. Also can be a side effect of some medications.
At least start there and have the Dr. rule out stuff so hopefully you can track down the cause 'cause bass playing' is too important.
Here's a link to get more info:
http://www.wrongdiagnosis.com/sym/cold_hands.htm IME, Wrongdiagnosis.com is a reliable place to check out medical issues.
Good luck.