Microtunings on the TX81Z
I've had one of these for a few years and recently picked up a second to keep it company, so I decided it was a perfect time to wrestle with the poorly-documented tuning implementation. I don't have anything novel to say here but I had to figure some of this out by trial and error so thought documenting it might help the next person out.
Use of Performances
A tuning can only be applied to a performance, not an individual patch or the whole unit. For some reason, although there are 32 user patch slots, the TX81Z only gives us 24 performance slots, so this is pretty limiting.
I don't have much use for the performances as splits or layers (especially with a pair of units) so I decided to set it up so that each performance consists of just the corresponding user patch assigned to all 8 voices with a tuning applied to it. This means that when I'm playing, say, patch 18 in Play mode, I can switch to Performance mode (with the Play/Perform button) and be playing the same patch with the tuning applied. Sadly you do have to click through to find Performance 18, but that's not so bad -- I wish the TX81Z had a rotary encoder for scrolling through patches but if it did half of them would probably be broken by now.
Philosophical reflection: the reason you're using a vintage synth with a glitchy little screen is that you want the limitations and the character that comes with it. Plus, 24 slots still gives you 23 more different sounds than Chopin's piano had and he did OK. So while it's possible to compare this unfavourably to working with VSTs in a DAW, I don't think that path leads to enlightenment.
Performance Setup
Here are instructions for creating a performance the way I like it -- a single patch with tuning applied. Honestly the menu system here is pretty intuitive so you'll probably be able to figure out whatever variations you want for your own setup.
First turn off Memory Protection, which is in the Util menu while in Play mode. This is something that foxed me at first -- the util menu works differently in the two modes, so go into Play, then hit Util and find Mem Protect and turn it off. If you want to, at the end of all this you can turn it back on again (I tend to leave it off, it's awkward enough to save a patch that I'm unlikely to do it by accident).
To start editing, hit Play/Perform to go into Perform mode, choose the performance you want to edit, then hit the Edit button. While in this menu you can use the Parameter buttons to move between pages. go straight to the P.ED MICROTUN page. Using the Cursor buttons, you can go back to change the =Oct at the top to one of the preset tunings or the keyboard one if you like. Then change off to on in all the slots for the parts.
If you want to set it up as a single microtuned patch, there's usually just one more step. Go to the page P.ED MAX NOTES and set the first slot to 8, which will put an asterisk in the others, indicating they won't be used. If you page through the rest of the edit menu you should find the asterisks appear everywhere else too. Of course you might also want to go to the page called P.ED
You also might want to rename your performance, but this is as miserable an experience as ever with a hardware synth and frankly I struggle to bother. Maybe one day I'll be bored enough to go through all my performances giving them the right names...
When you've finished editing the performance, remember to save it. Hit Play/Perform to exit edit mode, then hold Store/EG Copy, hit Yes to choose the save slot, release Store/EG Copy and hit Yes again to confirm. For the next one, if you're using my scheme, you can save again into the next slot and just change the patch number for Voice 1 -- in this way you'll get all 24 done in a few minutes once the first is set up.
Editing User Tunings
The TX81Z has two slots for user tunings but they're not the same. One is limited to octave tunings; the other requires you to tune each note of the whole keyboard. Personally I've only used the octave one so far, which means at any given time my units can play in 12EDO or one other tuning. On the upside, the octave tuning is relatively easy to edit, barring one annoying quirk.
Simply hit Util in Play mode, use the Parameter keys to navigate to the Edit Micro Tune? prompt and hit Yes. This takes you to a submenu where you can edit the octave tuning, re-initialize the octave tuning or edit the full-keyboard tuning (I don't know why you can't re-initialize that one, which would be much more laborious to do by hand!). I hit yes on Edit Octave? and you're into the tuning -- use Parameter keys to move between notes, and Cursor and Yes/No keys to pick which note each should be mapped to, with its microtonal offset. This allows for arbitrary tunings as long as they consist of 12 notes and repeat at the octave, so it's better than a lot of modern synths (even VSTs!) that only give you +/-50c on each note.
The quirk is that, this being an early digital device, it can't count up to 100 so it divides a semitone into 64 steps. That means an increment of 1 unit in the tuning menu it 1/64 of a semitone or about 1.56 cents. If you're tuning by ear that's probably not an issue but if you're trying to match a tuning given in cents you'll have to divide each value by 100 and then multiply by 64 to get the number of TX81Z units.
The in-between heuristic here is that 3 cents is about 2 TX81Z units, so 15 cents is 10 units, 30 cents is 20 units and so on.
Also remember that 64 is a power of 2, so if you want a power-of-two fraction of a semitone you can get there quicker. To drop a note by about 25c, that's 1/4 of 100, and 1/4 of 64 is 16, so drop it by 16 units.
If you change tunings a lot and need exact cent values this workflow will obviously be annoying. However, I don't believe anyone can hear the pitch inaccuracy that results. Maybe it's worth printing out a chart of frequently-used values if you'd find that helpful -- here's one I made earlier:
Cents 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 TX81Z 3 6 10 13 16 19 22 26 29 32 35 38 42 45 48 51 54 58 61 64
The service manual details sysex messages the TX81Z can send and receive, and among them is one for the microtuning:
This suggests that maybe we could build a bit of software that can transmit tunings on the fly. If I need a coding project next year I might have a go at figuring that out. If nothing else it would help to keep my units in sync with each other. For future reference, there are some clues about that here and here.
