Changing a melody from major to minor key, twice

Question

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?

Answer 1

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?

In terms of keys, you come back around to the starting key again pretty quickly:

C -> Cm -> Eb -> Ebm (D#m) -> F# -> F#m -> A -> Am -> C

There are four transformations from major to minor, and each one means lowering three notes, which means twelve total note lowering occur. The twelve lowerings are not evenly distributed across the twelve different note classes. Five note classes in your melody will be lowered twice each, and two will be lowered once each.

This means after coming back around to the starting key, the melody will have been lowered one diatonic step. In other words, if you start in C major, once you've gone around to C major again, every C will be a B, every F will be an E, and all the other notes will be lowered a whole step (D to C, E to D, etc.). The melody shape will remain intact but the tonality will be altered. If you keep going, the whole thing goes down another diatonic step every time you come back around to C.

Linking what happens to Divizna's answer, every time you come back to the first key you've moved the melody to the mode below the previous one. So the C major melody turns into B Locrian, then A Aeolian, G Mixolydian, etc. After seven cycles of four transformations, you'll be back in the original key and mode but an octave lower.

Here's a melody I transformed repeatedly in this way. Note that the initial melody uses every scale degree at least once and establishes C major as the tonality.

Answer 2

You end up in Ab Lydian. (Which is a major mode, by the way.)

A minor and C major aren't the same thing. The tonal centre, the "home" tone, is very much different. In A major, your tonal centre was A. In A minor, your tonal centre is still A. Now you put flats on B, E and A - and your tonal centre still isn't moving to C or Eb, it's just shifted by the flat you put on it.

Now, you can change key from A major to C major or Eb major or whatever major. This is called transposition. When you transpose a song, you move the tonal centre, while all the intervals are kept intact. The whole tune is just moved up or down, most often in order to fit a singer's vocal range. When you hear it, you aren't likely to even realise there's any change from the original at all.

But that isn't what you're describing here. Switching from major (Ionian) to minor (Aeolian) or Lydian or etc. scale does involve changing intervals, and the new tune is distinctly different from the original. You're creating a variation on the theme (which is a broader term that encompasses other possible changes than scale mode but I'm not aware of a more specific one).

Answer 3

Start in A major. 3 sharps. Losing those sharps, and playing the same name notes (which is what I think you're getting at), will take you into A minor. Not key C, although now, you have the same notes as key C. But the tonic is still note A. You haven't modulated into key C.

To do that, you have to move the melody so that it revolves around C, not A. You can, of course, do that, then change to 3 flats, still using C as home/base, and move on from there.

As far as naming is concerned, I guess it's using parallel keys, then relative keys. I'll leave you to work out which is which..! It's a ploy that's used a fair bit, in all kinds of music, so it's not a new concept, sorry.