Hey everyone! Just thought this link may be of interest to folks here: Surge Synth Team Tuning Guide
I’m on the Surge team, to be clear. Also to be clear, we’re a volonteer team and all our stuff is free, just so you don’t think I’m trying to sell you something. Anyway, that’s a page we have made to explain the tuning implementations we’ve made in Surge and our other products.
Few things to note:
In the most zoomed-out technical sense, there’s two approaches to making microtuning work. Either you modify the MIDI data going in to the instrument to play the tuning you want, or you change the midi-note-to-frequency function inside the instrument and leave the midi as it is. As you can see in that link, we generally prefer the latter approach, with MTS-ESP and scala files as our preferred standards. Pitch bend/MPE/Poly Expression can work well too, and some people prefer it.
If using MPE/PolyExp and microtuning, the important question to ask is how/if you want those two to interact.
Hardest thing to make workable is definitely pitch-slide playing, say on a Linnstrument. In an unequal tuning, sliding from field A to B might land you on a different frequency than if you played B directly. Tunings with more or fewer steps than 12 might get a bit unwieldy or too precise, etc etc. I don’t have a Linnstrument but am told that getting an intuitive play-feel for pitch slides is really tricky. Maybe some of the pitch-bend based tools out there can help with that. IDK. Definitely most software instruments with internal tuning don’t handle this particular case well.
On the other hand, you may be using MPE just for timbral expression, not pitch. In that case instruments with internal tuning will work great, I would just use those. Then the tuning is, so to speak, dealt with already and the poly expression can serve its main purpose of being expressive.
It’s also quite common that people otherwise not interested in MPE/poly expression want to use it only for tuning purposes. In my honest opinion the main reason to do that is if you have some synth you already know and love, which doesn’t have any other way of microtuning it.
If you’re not attached to using a particular synth, there are plenty nowadays with actual built-in tuning features. All approaches have their drawbacks, but pitch-bend based ones have definitely thrown the most wrenches in my wheels over the years, for what it’s worth. Though I do sometimes use it for a couple synths I love which don’t have MTS-ESP (Izotope Vocalsynth, Madrona Labs, etc).
Good luck exploring!
