Having seen that there are requests for alternative scales, here's a 'trick' to get alternative equal temperament scales, using the keyboard tracking to stretch or squash the scale. It has to be done per patch though, so this method won't be a quick way of changing scales for any given patch. Here's the recipe for 24 notes per octave, where we need to squash the scale to give us quarter note intervals between the keys :
First make sure that your MxB is warmed up and tuned - leave the synth on for 30 minutes, then use the auto tuning feature if you haven't done that yet (or in a while).
For VCO 1 and/or 2:
- assign Kbd/Seq to VCO 1 and/or VCO 2 pitch, set the mod values to -70
- assign M1 to VCO 1 and/or VCO 2 pitch, set the mod values to +99
- set M1 to +14
This setup needs some serious fine tuning, but it's not hard. Do it one oscillator at a time. Use another synth as your pitch reference and tweak M1 (our tuning value) until the bottom C is in tune with the bottom C on your reference. Then tweak the Kbd/Seq to VCO 1 mod value (our "stretch" value so that the MxB's C two octaves above the bottom C matches the reference's C one octave above its bottom C. Repeat this procedure until everything is perfectly tune. It should be done in less than 10 iterations since you've got the starting values pretty close already.
Remember that there's many actual steps for each number in the LED display, so use a steady hand for the fine tweaking.
For VCO 3, which differs in that it hasn't got a pitch column in the mod matrix, so we need to use its coarse tune instead:
- assign columns 13, 14 and 15 to VCO 3 Coarse
- assign Kbd/Seq to columns 13, 14 and 15, then set their mod values to -99, -99 and -70
- assign M2 to columns 13, 14 and set their values to +99
- set M2 to +38
About spending 3 assignable columns just for VCO 3: this can be skipped if you don't use VCO 3, or if you use VCO 3 as an LFO with key tracking off (or even with key tracking on if you don't mind a different key to LFO rate relationship across the scale than for the default 12TET tuning).
The reason for the triple assignment of Kbd/Seq to column 13,14 and 15 is that we need to add up more than one maximum mod value to get the required range, and we use the last one, column 15, for the fine stretch tweaking. The same goes for M2 to columns 13 and 14, where we use the M2 macro knob for the fine tuning. Other than that, follow the same procedure as for VCO 1 and 2, only using M2 as the tuning value and the Kbd/Seq to column 15 mod value as our stretch value.
Here's a tabular view of the mod matrix setup:
1 5 13 14 15
VCO 1 VCO 2 VCO 3 VCO 3 VCO 3
Pitch Pitch Coarse Coarse Coarse
-----...-------...-----------------------
I Kbd/Seq -70 -70 -99 -99 -70
M M1 +99 +99
N M2 +99 +99
M1 macro knob = +14
M2 macro knob = +38
If you want more that 24 notes per octave, reduce the -70 values further until you have the required scale-squashing, and vice versa for fewer notes. The M1 and M2 tuning values would also be different.
Attached is a patch, "Init24", which applies the above tuning to all three oscillators. It's the same as the normal Init patch, just with the 24 notes per octave and all 3 oscillators going. Remember that the MxB oscillators are fully analogue and the mod values may be slightly off for your synth compared to mine, so tweak until properly tuned. The MxB oscillator tuning is very stable, so once you have your own tweaked version of Init24 (or whichever number of notes) it should be reusable.
The "Init24" patch has been updated as VCO 3 was tuned an octave above VCO 1 and 2. The original could be pulled into tune by tuning VCO 3 Coarse an octave down though. Sorry for the inconvenience.
Edit: I thought I should explain why the Macro Knobs are being used to bias the tuning. It's because that allows the base patch to keep the coarse and fine tuning at their normal middle positions which makes it easier to work on the actual sound when dialing in intervals between the oscillators. You can skip the use of the Macro Knobs for this and tune with the coarse and fine tunings instead, apart from VCO 3 which may not hit the precisely correct tuning since it only has the coarse knob. Macro Knob 1 as used for VCO 1 and 2 can definitely be skipped if you prefer to free up one macro knob and are willing to run with the tuning knobs at whatever positions it takes (you can use Macro Knob 1 for VCO 3 in this case, so that only the innermost macro is used for further knocking-out-of-whack protection). Do what suits you best - it's easy to set the tuning bias, the fiddly part is to get the stretch values from the keyboard tracking right.
