One more question which I hope will make things clearer for me…

Scales - you can obviously have different ones. I get that a track written in say C Maj is gonna sound pretty upfront and well maybe cheesy

So you could decide say on using something more subtle - eg A min

That then gives you access to 7 / 8 notes right? I also understand how to apply to major or minor pattern of intervals to work out the corresponding notes in the scale

I even know how to work out the triad from the scale (yep, it ain't difficult) to give you the chord of that scale.

But what I do not understand is how this relates into chord changes. Say I used the scale of A min, say I worked out the chord to be consisting of A, Cb, E (for example) - when I wanna progress the chord to another, doesn't that throw the A min scale outa the window?

Or, if you work out work the next "proper" chord is, because it "works" does that mean it still fits with the scale you use?

I suppose what I'm asking is how many scales do you use in one piece of music? Is it just the one???

This is hard for me, my brain is frantically trying to forge new neural pathways but hell there is a lot of resistance!