If you want to improvise over a chord progression in the key of C-major, obviously you could improvise with a C-major scale. My question is this, if you want to improvise with a minor scale over a major chord progression, do/can you use A-minor and/or C-minor?
I'm guessing (with my admittedly limited understanding of theory) that you should only play A-minor scales over a C-major chord progression and a C-minor scale should only be played over a chord progression in Eb-major.
Any clarification would be great. Or am I totally talking nonsense and the question isn't even correct?