I bet the cortex, including the audio cortex contributes more to music enhancement when it comes to psychedelics and cannabis that can alter the perception of music. There could also be effects on the medial geniculate nucleus, the brain's auditory thalamus (relay/filter).
Effects on these various areas could modulate the transmission of information to the "reward" areas of the brain. I believe people with depression have reported under appreciation of music and that correlated with low activation of these reward areas.
It could be that the rewarding properties of music occur moreso in the reward areas but that activation of reward associated areas that occurs in a rewarding manner could be very dependent on the input from cortex/medial geniculate nucleus/inferior colliculus.
With cannabis you have THC binding to CB1 receptors that causes alterations in release various neurotransmitters and altered neurotransmission, but at the end of the day it's probably still increasing dopamine in reward associated areas like the nucleus accumbens (in addition to modifying the input to this area by modifying the transmission between the audio cortex and so forth). So the cognitive interpretation of the audio is different, and this could add an element of novelty (which can often be rewarding).
