Assuming that there are different processes going on in my brain while listening to these two intervals, I'd like to know: What are the qualitative differences between these processes that would allow to understand that the first is experienced as pleasant and the other is experienced as unpleasant.
Just by thinking about it, there seem to be three possibilities:
The same regions/areals/neuron groups are active but in different characteristic modes, exhibiting different spatio-temporal patterns of neural activity.
Different regions are active in different modes.
Different regions are active but in somehow similar modes.
Assuming that the difference is mainly due to different activity modes (cases 1 and 2), I would like to know which characteristics might correlate with the pleasantness and unpleasantness of the expericence, e.g. some kind of "harmony".