I was [jamming](http://www.multiplayerpiano.com/) with some jazz guys yet I'm not so good in jazz so I made a bunch of mistakes. One of the things they told me is is how inside of a chord progression, you then spread each chord to its associated scale. So if you have a four chord progression, you could potentially have four different scales. And I never came across that before. One guy even told me it's "spicy" to flatten certain notes of each scale as well.

So I was wondering what the theory is in regards to this. How do you turn each chord into its scale. For example, let's say I have the I-IV-V chord do I then play/pick notes from the associated major scale of each one of these. And then for ii,iii,vi you play the associated minor scales? Are there rules then as what to flatten? Or other rules in regards to certain chords, like dominant seventh chords, or other chord types how do you turn those into scales, do you just randomly pick what scale contains those notes or is it more to it? And when you have the a new sub-scale can you then turn to new chords inside of it.

I tagged this as jazz, but I'd like to apply this theory to other genres as well. I mainly play movie soundtracks, video game music (hence my interest in jazz), pop, new classical, stuff like that.