For those who are familiar with musical notation, that is an option, but even so there are some weaknesses to that scheme and it is very opaque to people who do not understand it.
There are no good tools for people who want to use xenharmonics. Or if there are, I haven't found them in well over a year of looking.
After many months of thinking hard about how such a tool would look, I recently had a breakthrough and discovered that a lot of people have been asking for it, mostly without being able to explain why. Here I'll describe what it looks like, and even give some ideas about how a current tool could achieve that.
The basic core approach is the pianoroll. Why? Because it has certain key valuable elements:
- Every note's relation to the height of every other note is visible at a glance.
- Every note's duration and position on the timeline is similarly visible at a glance.
- With the use of intensity/saturation/contrast, every note's volume is visible at a glance.
- Allow lines to bend up or down, and you have portamento/slides.
- Allow lines to fade in and out, and you have envelopes, volume automation, crescendo and decrescendo control.
- Allow lines to snap to grid for quantisation, but then allow those grids to change along a timeline, and you have tempo control for your song, as well as time signature control.
- Allow the vertical grid to be modified, perhaps even during a song, and you can change from snapping to the regular western 12TET scale to renaissance era just intonation, or 17TET classical arabic, or a strict diatonic or pentatonic or any other scale. Xenharmonics become practical, even approachable.
The idea is not to make a full scale synth tool out of it (although some prepared sounds would be convenient) so much as a sketchbook for the kinds of composers who plan their work in detail. The grid lets composers plan intervals and even complex chords and progressions. Letting the grid's structure change within the piece allows for complex time signatures, key signatures or even complete scale shifts. A composer would use it to hammer out a structure, and then turn to some other tool (Sunvox, or a full scale DAW) for production. It's like the electronic equivalent of a music notebook, or a guitar for hammering out chords and harmonies.
And, NightRadio, if you did it for real scale changes? You'd basically have the total worship of the xenharmonic community. You would undergo apotheosis. There is no credible competition. Or at least, if it exists, it's the world's best kept secret.
So, I propose PixiRoll. A scale line on the left, which is modifiable either by the song or ideally within the song. Timeline along the top or bottom. A small sound selection as per pixitracker, or the VirtualANS palette. Different instruments have different icons/colours. Snap to grid, but allow for bending. Also allow for volume shifts. I wouldn't necessarily bother with stereo, because this is more of a planning tool than a true production tool.
Maybe I'm completely underestimating how difficult all this is, but I think it's well within the kind of thing you've already done. One thing I know I'm not underestimating is how fervently the insane xenharmonic underground wants this. And it would be convenient for regular old composers who just want to plan their 12TET pieces, or switch between 12TET and just intonation.