Say I have a chord progression in C major:
I V vi
C G Am
When I play each of these chords can I potentially play the scale of each chord over it? So for C I'd play C major, for G I'd play G major, for Am I'd play A minor scale. I'm thinking this is possible because secondary dominants work this way by establishing a temporary key on whatever chord you're currently on. But does this happen in practice where people modulate to a different key on each chord change?
Edit: I was confused that a scale can be played over a chord. I thought the moment you play a scale then you're in a new key. I forgot that in order to establish a new key you need to atleast play a progression in the new key. It's just that I saw a video and they were playing different scales over each chord and it mixed me up. I forgot a scale wasn't the same as a key.