What is the definition of the expression "you are churning it", other than its literal sense? I heard it in the context of someone playing music.
Was it said as praise or as criticism? Makes a difference :)
Rock music or experimental... ? Amateur/semipro/pro? Which instrument?
Churning means, I think (too lazy to look in a dictionary) stirring cream until it turns to butter. So it's a repetitive motion and one that is confined to the same space.
There are a number of metaphorical uses... one is as a derogatory term for an unethical practice in financial management, when a money manager turns over your assets repeatedly in order to collect on transaction fees.
In improvised music, especially modal music with little harmonic movement, a musician might be noodling around in the same mode for some time and appear not to be "going anywhere", at least not harmonically. This is a kind of lateral movement and possibly "you are churning it" refers to this; it doesn't sound too complimentary. Then again, it could perhaps be a complimentary remark if that's what is desired.