
Jake R. answered 07/01/19
I want the best for all my students.
In my opinion,
the origin key is most likely C mixolydian or C Blues. A song with that much movement from dominant 7s must be particularly unstable and wouldn't sit naturally in a major or minor key in a traditional sense. Each chord in the progression has its own chord scale, which is chosen based off the notion of picking a scale that is most related to the scales that come before and after it in the progression. This means having the most notes that are present in both keys when comparing two chords that are adjacent. This is probably a jazz tune, which is modulating through a sequence of mixo scales from the root of each chord in sequence. The melody will also serve you in revealing the key, so focus on which notes and tones are most emphasized within that!
Best,
Jake