Negative Tuning on the Prophet VS

One of the items on the VS wish-list from Jason Proctor (Vector Surgeon VS Editor/Librarian) is negative tuning values. In the stock OS, Coarse values range from 0 to +24, and Fine values range from 0 to +99. This ultimately makes all de-tuned patches slightly sharp. [Edit: Or, like SCI did, you can do a "negative" tuning by setting Coarse: 11, Fine: 90, for example]

I figured out a way to do this, but it's not a simple change.

You can see that the positive values are still stock, which gives 5 octaves of tuning range compared to the original 3 octaves. I did this expecting to keep factory patches compatible (eg if the original patch was set to +20, it would still be +20) but that was a dumb assumption. As the video shows, this works fine in the edit mode, but it is unsaveable as a patch.

The VS sets the bit-depth of each parameter as it saves & loads based on an array in the code. Here is the MIDI chart compared with the stock bit array:

In order for the VS to save a negative tuning value the # of bits has to be 8, for a signed parameter. The issue is that once any of these values change all internal patches and even sysex becomes corrupt since the bits are being unpacked incorrectly.

There are a few options to make this work though:

1. Rebuild the factory set by hand to be compatible with the new scheme. This would make it harder for people with their own libraries & patches.
2. Include a power-on diagnostic-style routine that loads whatever is currently in parameter memory with the correct bit-unpacking, then re-save with the new bit scheme. Users would load their sysex (it would look corrupt), restart into this mode, then resave. I am not even sure this would work, but I'm gonna give it a shot.