For me for example, much of reality is acoustic ; it is melodic and tonal because I have poor vision from birth. I have poor hearing too but I had early piano training which “digitized” and melodized my view of reality.

So, I’ve been going through various neural correlates lately, and I found how much of music is linked to motor systems; so when I am imagining new melodies in my head, I’m actually recombining existing motor patterns used by my fingers in novel ways and rehearsing via the Pre-SMA; it can only use existing patterns but they can combine in many ways and it’s always possible to learn new patterns to then incorporate in future branching possibilities.

But it only combines “one at a time”; that is, one complex motor action (or melody) follows another; so improvisation is a series of limited forward thinking modifications whose final output can’t be predicted because it’s constructed along the way; yet it’s constructed of already known parts and can happen just under the level of awareness; that is to say it can ‘feel as if’ the muse is taking over (hence the word Music), although one has control at that stage; it’s just that the grammatical systems are a tiny bit slower than the motor systems.