Here, the walls are a foot thick; one neighbour says they can't hear anything and the other has not mentioned bass practice, but does have a dog that can be heard barking and howling frequently through my living room wall. If they can hear anything then I think that makes it even.
I am reminded of a singer I performed with once (that gig came up in a "worst ever gigs" thread) who awoke his neighbour by putting up a picture on an adjoining wall at around 3-4am. The neighbour came to his door to complain and, upon being told to f**k off, punched him.
When the police then arrived at the singer's summons they found his flat to contain a significant number of road signs etc., resulting in a charge of "theft of street furniture".