After some experimenting with creating a standard tuning with different labels, so we can get something of a flat-key system, as opposed to the omnipresent sharps, i came up with something that might work. I only tried this in the .mptm format, and it worked okay.
1. Set up a new .mptm track file, or convert another to the same.
2. You must use an instrument to set up non-standard tunings, so if you're starting with a new file, create a new instrument (it doesn't have to have an associated sample).
3. In the far right hand side of the instrument panel, click the Tuning Menu and select "Control tunings...". A dialog box will appear with many fields. On the left is a list of tuning files, most of which i don't understand. I do know that "Unnamed" is a copy of OMPT's default standard tuning table.
4. The object here is to take a standard tuning file (we're not tinkering with the actual acoustics) and create new labels. So select the Unnamed standard file and, if you like, rename it in the Name field. I renamed mine "D-flat scale".
5. Select one of the notes at the right labeled A:1 or so. Each of these are actual labels as the code sees it. I found that A:-7 is C4. Relabel any note name by clicking in the notename field at the bottom.
6. LPChip was right -- there are limited characters you can use for your label, and 'b' isn't one of them. Altho they will appear fine in the note menus, they will not contain the right characters in the note data columns, where you need to see it. So until the devs change the bitmap, i use the \ character to represent the flat symbol. When renaming the notes, remember to assign the right octave, such as C 4, D\4, D 5, etc. Also, to line up the octave column, put a space or period between the natural note tone and the octave number, such as "C-4".
7. When you're all done, use the EXPORT button to save this tuning.
8. Make sure you've selected the correct tuning in the Tuning menu (whatever you named it), but keep in mind that you have to select this tuning FOR EVERY INSTRUMENT -- it's not a global setting. This also means that every note played that's not triggering an instrument will revert to the default tuning (OMPT's sharps).
As a side note, i couldn't get the Save button to work in the Tuning dialog box, but the Import/Export buttons worked fine.
Also, there is a glitch in the A:5 label, which will cause all unnamed notes to use this label ("A:5") and any additional characters after the 5. Kinda hard to explain, but you'll see it once you begin relabeling the notes.
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After further experimentation, while this worked great when VSTi's use the track, actual sample acoustics must be calculated when using samples, or all the notes will play the same tone. If i remember correctly, you have to set the Step(?) number to a strange number like 1.041 or so (square root of 2?). I played a scale in the pattern editor while i fixed the acoustics and this worked out the correct tones...more experimentation forthcoming....