Tuning RPNs: Difference between revisions

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So it would be great if there was a simpler, non-sysex way of tuning individual notes. A few of us have cooked up a daring plan. The powers that be will probably never give us what we want, so we'll just __take__ it! We can commandeer an obscure and underused part of the midi spec and use it for our own microtonal purposes. We can simply create a new unofficial microtuning method. By "we" I mean the authors of midi tuning software. If we all include this new method in alt-tuner, Fractal Tune Smithy, Custom Scale Editor, Scala, LMSO, etc. we will have a more enticing sales pitch for synth developers and designers: Add this simple easy method of retuning and you will sell more synths to microtonalists.

The new method uses RPNs (Registered Parameter Numbers). The technical details: There are about 16,000 possible RPN parameters, and only about a dozen are in use. We can use a block of 128 RPNs, one for each note number, for retuning. Data MSB and LSB messages for these RPNs contain the cents to retune by, in the exact same format as the standard midi pitch bend message. The retuning is immediate (real-time), just like the standard pitch bend. This makes it easier for the synth developer or designer, because he has already written code that deals with physical pitch bend wheel movement, and can just reuse it to deal with tuning RPNs. We use either a data increment or a data decrement message to transpose the input note by so many semitones, allowing for non-12-note tunings. If the RPN MSB is 100 = 64 hexadecimal, then to bend note nn on channel c to note mm with bend of yyzz would take up to 5 midi CC (Controller Change) messages. In hexadecimal the midi looks like this:

So it would be great if there was a simpler, non-sysex way of tuning individual notes. A few of us have cooked up a daring plan. The powers that be will probably never give us what we want, so we'll just &lt;u&gt;take&lt;/u&gt; it! We can commandeer an obscure and underused part of the midi spec and use it for our own microtonal purposes. We can simply create a new unofficial microtuning method. By &amp;quot;we&amp;quot; I mean the authors of midi tuning software. If we all include this new method in alt-tuner, Fractal Tune Smithy, Custom Scale Editor, Scala, LMSO, etc. we will have a more enticing sales pitch for synth developers and designers: Add this simple easy method of retuning and you will sell more synths to microtonalists.&lt;br /&gt;

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The new method uses RPNs (Registered Parameter Numbers). The technical details: There are about 16,000 possible RPN parameters, and only about a dozen are in use. We can use a block of 128 RPNs, one for each note number, for retuning. Data MSB and LSB messages for these RPNs contain the cents to retune by, in the exact same format as the standard midi pitch bend message. The retuning is immediate (real-time), just like the standard pitch bend. This makes it easier for the synth developer or designer, because he has already written code that deals with physical pitch bend wheel movement, and can just reuse it to deal with tuning RPNs. We use either a data increment or a data decrement message to transpose the input note by so many semitones, allowing for non-12-note tunings. If the RPN MSB is 100 = 64 hexadecimal, then to bend note nn on channel c to note mm with bend of yyzz would take up to 5 midi CC (Controller Change) messages. In hexadecimal the midi looks like this:&lt;br /&gt;