Synth tuning using keyboard split

I wrote :
>>
>>Just using a keyboard with atleast one split point, it is possible to
>>fool around with many equal temperaments. I've been giving it a bit of
>>thought and it should handle equal temps of upto 24 notes per octave.
>>All it entails is transposing both left & right sides to the same
>>"octave" range,
>>then tuning the both parts to the odd numbered pitches of an ET, and
>>shifting
>>the channel master tune so the pitches on the right hand become the even
>>numbered pitches of the scale.

John L. wrote :
>
>You could do quartertone scales this way, but not any other nTETs.

If you get creative with it and agree to cope with remembering which
key is what,
it is possible to get many tunings with more than 12 note this way.

It's not quite as simple as tuning the odd notes, and shifting to
get the even notes, i.e., it doesn't work that simply for just any
tuning.
It does work for 19-tET.
You need to take the gist of the idea and play about with it. For
example,
here's how to tune the first 18 notes of Wendy Carlos' Alpha tuning.
(I've also done 19-tET & Wendy's Beta. Gamma is not possible with
only one split.)


The first column lists the first 18 notes, the second column lists the
microtuning for the named keys, and the third column first shows that
you have to shift the channel master tuning right hand side of the split
up 234 cents and lists the cent values this results in.
(This can be done by first coarse tuning up 2 semitones,
and then fine tune up 34 cents. On the Yamaha PSR--530 use the RPN
Fine Tune parameter values : MSB=104, LSB=0.).

All units are in cents. The squiggly lines are to try and keep things in
their place.


Alpha,~~~~~~~~~"scale tuning"~~~~~~ PartShift
First 18 notes~~~~key name~~~~~~~~~~(+ 234 cents))
0~~~~~~~~~~~~~~~~~C~~~~~(+ 0)~~~~~~234
78 ~~~~~~~~~~~~~~~~C#~~~~(-22)
156~~~~~~~~~~~~~~~D~~~~~(-44)
234
312 ~~~~~~~~~~~~~~~D#~~~~(+12)~~~~~~ 546
390 ~~~~~~~~~~~~~~~E~~~~~~ (-10)
468~~~~~~~~~~~~~~~F~~~~~~( -32)
546
624~~~~~~~~~~~~~~~F#~~~~~(+24)~~~~~858
702 ~~~~~~~~~~~~~~~G~~~~~~ (+2)
780~~~~~~~~~~~~~~~G#~~~~ (-20)
858
936 ~~~~~~~~~~~~~~~A~~~~~~(+36)~~~~1170
1014 ~~~~~~~~~~~~~~A#~~~~~(+14)~~~~~1248
1092 ~~~~~~~~~~~~~~B~~~~~~(-8)~~~~~~1326
1170
1248
1326

Please let me know if I've done something silly again.

BTW, as mentioned in my other post the PSR-530 holds a different scale
tuning on each channel, expanding the possiblities further.

Cheers,
Drew

Hi Drew, thanks for the good info!

Drew wrote:

>Pitch bend, I checked with the range at 1-semitone and
>found no clear pattern in the data values that caused each successive
>pitch change.
>Graham Breed mentioned he does this and
>David Finnamore posted a note cautioning about it, you HAVE to check
>the frequency of the bends against actual cent frequency equivalents.

For those of us without a frequency meter, old-fashioned beats can be used.
Here's my favorite trick for making sure I'm in tune when stretching the
capabilities of my O5R/W, which, like Drew's Yamaha, uses some tuning-related
SysEx implementations that seem to defy logic:

First, select a tuning table that you are certain about for one channel, like
Pythagorean or 12-tET. Sound a long note on that channel, tuning it with the
channel's Detune parameter to the target tuning's pitch for that note.
Simultaneously, sound the same long note on another channel using the target
tuning/transposition, and listen for beats between the two notes. Using a
pure sine wave on both channels is most helpful.

A related method worked well this past week when I Just-tuned (mostly 5-cap
sprinkled with 7-lim consonances) a MIDI file of an old 12-tET orchestral
instrumental of mine, which modulates from Ab to C#m, back to Eb, and then,
over the course of about a minute, through F and E to end in G#. The G# is a
double syntonic comma - nearly a quarter-tone - south of the original Ab!
Kind of stretches the ear a bit, but it sure is nice to have all those pure,
resonant vertical intervals.

The bass line (almost all roots) was on Pythagorean-tuned channels, and stayed
Pythagorean except at the points of the last two modulations, which were by
15:16, and so needed to be shifted down about 21 cents each time. After
tuninging the bass tracks properly, I duplicated the bass line on a Just
track, adjusted its channel Transpose and Detune parameters (first by "the
numbers" and then fine tuning by ear) at each mod to keep it in tune with the
Pythagorean track, then used trial and error to find the SysEx messages needed
to set those parameters automatically during playback.

Thankfully, Korg's pitch bend implementation seems to be perfectly consistent,
allowing the use of the formula cents*8192/P.B.Range to tune individual notes
on the fly on monophonic tracks. It's surprising to me that Yamaha's
implementation is less reliable.

Those cheesy brass and wind samples that most of us have to put up with sound
a lot more realistic when they're in tune! Maybe that's a good place to start
when demonstrating the value of tuning to other keyboard players.

David J. Finnamore
Just tune it!