i have to use both,,,
i get the imagination by feeling the song...
and i feel the song by using my imagination...
sounds pretty confusing..
but that's the way i do it.. (=_=)

I mainly let my imagination flow, whenever I listen to music. It is true, however, that some genres of music suit, better than others, this unusual "stream of thoughts".

VGM can work in different ways.
1) One could have a remembrance of what moment (in the game) is associated to that specific track.
2) Or, different images, that have none to do with the game itself, could be mentally associated to the tune.

Personally, I do both - but, for me, tracks that are more melodic *do* adapt more to the latter.