How to create a 15edo tuning in Logic Pro X?

Hey, in case you still care to know this, I have been using Logic Pro X as a tool for microtonal music for some time.

I am unaware of any straightforward way to allow more than 12 notes per octave, so this is a bit of a workaround.

First, you’ll want to go to File > Project Settings > Tuning. You can set custom tuning as displayed below.

These are parameters that worked best for me; they are a subset of the 15edo scale. If you only need twelve notes, this is all you need to worry about.

When I need access to more than twelve notes at a time, I split the keyboard at middle C, and I use the two halves of the keyboard like they overlap and give me up to 24 distinct pitches. That way I can plug into my standard digital piano keyboard and play all the notes.

To do this, I duplicate the software instrument I intend to use, and I put both in a track stack. Within the track inspector for each instrument, I restrict the range to be mutually exclusive. Here, I have set the range to be C3 and up, whereas the other harpsichord instrument in my track stack is B2 and below.

Then, I tune them apart from each other one step in whatever edo I mean to use—for 15edo, you could tune one of them 80¢ off, or you could tune each 40¢ apart. (Most software instruments will have a tuning knob.) You can then add a transposer to the instruments so they both play in the intended range—usually I transpose the left-hand keyboard two octaves up and the right-hand two octaves down.

In the end, you end up with two half-keyboards one step apart. A little hacky and not super intuitive to play either, but hey, it’s the best I could figure out. From what I understand, the MIDI standard makes encoding >12 pitches per octave difficult from a software perspective. Hope this helps!