Melakata Tunings
So I had this weird idea of taking the Carnatic melakatas, which are 7-note scales, and mapping them onto the white keys of a piano keyboard. Then tuning each black note to be exactly between the white notes either side of it. By this method we get 12-note subsets of 24-EDO that are maybe interesting or fun to play with? I don't know.
For example, Senavati is 1 2 b3 4 5 b6 bb7. If we map that to the white notes we get C, D, F and G unchanged; the key E actually plays the note Eb, A actually plays Ab and B actually plays A. Now we fill in the black notes. C#/Db stays the same. D#/Eb becomes E half-flat, because the white notes either side of it are D and Eb. F# stays the same. G# becomes G half-sharp and A# becomes A half-sharp. So altogether here are the twelve notes in this tuning, written with sharps and t for half-sharp: C, C#, D, Dt, D#, F, F#, G, Gt, G#, G#t, A. That looks like a mild diversion from 12EDO, since it swaps out three of its notes for three quarter-tones but it's pretty spicy when you play it because of the way the notes are bunched up.
You can download all the resulting Scala files here as a zip file -- look under scala/melakata_tunings for the ones in this post. On some instruments (e.g. Pianoteq, AAS stuff) you'll need to set the reference note (aka the "diapason") to be C (261.6 Hz) rather than A (440 Hz), otherwise it won't map the notes as described. This is actually a cool feature to have but it's confusing if you don't know about it.
I can think of three neat things about this seemingly ridiculous exercise.
First, you can now play any melakata you like using only the white notes. I know that sounds lazy but there are 72 of them and maybe you just want to try them out quickly without having to learn them. You can also "transpose" any MIDI file that uses only the white notes into any melakata you like simply by loading up a different Scala file, which is a bit of a niche thing to do but it might prove useful. So these are quality-of-life tools for folks who want to play around with Carnatic melakatas without getting in too deep.
Second, every one of these is a quarter-tone scale; that is, it's a 12-note scale from 24-EDO. That means if you're into space-age quarter-tone sounds these are more weapons for your arsenal, except instead of being very symmetrical and balanced like the ones I've investigated previously, these are lumpy and weird, but comprehensible because 7/12 of each of them is a melakata. So these are new resources for quarter-tone composition that still have a foot in familiar ground.
Third, playing just the black notes produces pentatonic scales from 24-EDO. There are so many of these they'll make your head spin, but these tunings are nice way to encounter some of them because you can "touch down" on something resembling solid ground; the white notes that hold the melakata. So these are also a launchpad for exploration into the outer reaches of the quarter-tone universe.
Are they actually useful for any of these things? I'm not sure, but I've been playing with them for the last couple of weeks and got mixed results, depending as usual on how much time I spend with each tuning. I'll certainly go back to them when I'm looking for 24EDO sounds I can use in the future, and perhaps also when I want to muck about with melakatas in a different way.
One thing that might be useful is a set of tunings that give all the notes from 24-EDO that are not in each of these, so you can set up two keyboards and get different splits between them. But there are probably a handful of people who'd be interested in doing that so I'll save it for another post.