A Ukrainian engineer Oleg Berg has found a way to change the key of a song from major to minor and vice versa, thus transforming its effect on the listener by completely altering the mood.
Here is an example that uses one of the Beatles classics Hey Jude switched from the original major to a minor key.
My verdict on the net result? The new version sounds terrible. Maybe this works better for songs where you are not that familiar with the original. R.E.M.’s Losing My Religion sounds better to me in the revised major key. Anyway, you can decide for yourself.
However, I found the technical achievement to be impressive, especially the fact that the voice still sounded like Paul McCartney, even as the notes he was singing changed. A friend of mine who is extremely knowledgeable about music (and is a huge Beatles fan to boot) explains what he thinks was done.
There is apparently a program called Melodyne (Celemony Melodyne) which reverse-engineers an MP3 into individual notes. It’s essentially parsing a full-spectrum recording to musical ‘atoms’ (which is almost already done, because MP3 is sort of a compressed Fourier transform of the music already). Now each atom can be classified as a particular note. It won’t be exact, because there’s bound to be a little wobble in the note. The really clever part is how they manage to decouple notes that are sounding concurrently! I mean, we have known how to do harmonic analysis for years, but how do they apportion the sound spectrum between the various instruments?
At any rate, once this has been done, I think it is not difficult to, more or less automatically, replace all the occurrences of, say, E natural, to E Flat, and similarly for any other notes that would be different in the one mode than the other. Now, they have to go back and fine-tune certain notes, because a minor scale uses one note sometimes, and another note other times.
NPR’s All Things Considered had a piece on this with some additional examples that you can listen to here, along with an interview with the person behind this, and some discussion of how changing the major/minor key strongly affects the way we perceive the music.