I thought of an interesting idea but I have very little music theory knowledge so I don't know how to look up additional information about it.
The idea is the following: Say I have a melody in A major key. It's some happy tune. If I want to convert it to a minor key I can do that by lowering the third, sixth and (let's say) seventh notes in the scale. To me the melody usually changes to a sadder tone. Now, all the notes in the melody could just as well be interpreted as if they were in C major since it contains the same pitches so I wondered what would happen if I converted it to a minor key again. From C major to C minor.
I've tried this a couple of times and I think I get a different melody from both the original and the second transformation. I could presumably just keep going repeating the same method. What would happen to the melody?
To make this a concrete question, is there a name for this process and is there any use for it in music?