RCT

[mitchkiel@olywa.net]

Jim Coleman wrote here on PianoTech:

>With the advent of the RCT, again Six (or Five) notes are sampled in order
>to control how the various octaves relate to each other. There are 10 
>basic tuning curves available to readily select, plus a customized curve
>which the tuner controls completely. 

  Reyburn CyberTuner (for both Windows and Macintosh) has 
ten pre-set overall stretches called "Octave Tuning Styles." 
They vary from barely wide to extremely wide, and are chosen 
by simply clicking an on-screen button.
   But Jim misses a crucial point: RCT does not have "ten basic 
tuning curves." Instead, RCT has ten stretch settings that react
differently to every piano. Therefore, the number of RCT 
tuning curves is actually 10 times the number of existing piano scales!
Furthermore, Custom EQ lets you alter each of OTS in thousands of 
ways, and therefore RCT can create a virtually infinite 
number of tuning curves.
    Because you can create and save 10 customized OTSes in Custom EQ,
 it's most accurate to say that RCT gives you 20 preset stretch styles,
10 of which you can customize and re-name anytime.  

   There's lots of smarts inside RCT's Octave Tuning Styles.
 Each Octave Tuning Style (OTS) has five specifications:
1. beat speed of A2-A3 as a 6:3 octave
2. beat speed of A3-A4 as a 4:2 octave
3. octave type of A7 (from pure single octave to pure triple octave)
4. maximum allowable beat speed of double octave A2-A4 as a 4:1
5. minimum allowable beat speed of A2-A3 and A3-A4
   During the fraction of a second it takes RCT to calculate a tuning, 
it uses the 21 partials it's already recorded from A1, A2, A3, A4, A5, 
and A6
to directly and precisely calculate the beat speeds of A2-A3 as a 6:3, 
A3-A4 
as a 4:2, and A2-A4 as a 4:1. We call RCT's method of directly
comparing partials "virtual direct interval tuning," which is 
exactly how aural tuners listen to pianos. 
   After calculating A2-A3, A3-A4, and A2-A4, RCT checks to see if 
the beat speed of A2-A4 is greater than its allowed limit (#4 on the 
above list). 
If not, the tuning is calculated. But if A2-A4 exceeds its Double Octave
Maximum setting, it narrows A2-A3 and A3-A4 until A2-A4 is within its 
limits. 
Then it checks A2-A3 and A3-A4 to see if they're *less* than their 
allowable minimum (item #5 on the list); if so, A2-A4 is expanded until 
item #5 is satisfied.
   You might have noticed these are the same steps aural tuners use if, 
for 
example, they use the Baldassin-Sanderson two octave temperament.
    As I hope you can see, RCT tunings are calculated using *aural* 
principles and 
techniques, which is why RCT tunings sound so good and why I far prefer 
it over
any other ETD I've ever used.
    
    Jim then refers to RCT's Custom EQ, which is where you can 
micro-adjust
the stretch of every octave of every OTS by as little as 0.02 bps. 

>A newer version of the program has added
>real slick graphics so that one can see what is going on in all of the basic
>octave matching relationships of the A's on  the piano. 

    Custom EQ's graphs lets you preview 88-note graphs of the widths (in 
beats or cents) 
of octaves (12:6, 10:5, 6:3, 4:2, and 2:1), 4:1 double octaves, 3:2 
fifths, and 3:1 twelfths.

>This still does
>not in reality deal with the note to note relationships between the A's.

   Jim, if I correctly understand what you mean, this is incorrect. 
Custom EQ interval graphs are created using the actual cents 
readings for each note that have been calculated by RCT. 
This means that each interval width is calculated using the same cents 
setting
and the same partial as you'll tune it to. Therefore the interval widths
that are displayed on the graphs are the *actual* widths, and 
are correct for all displayed intervals whether they include an A or not.
   Jim, I apologize if I've misinterpreted what you meant to say here. 
If you meant that RCT doesn't directly *sample* all 88 notes, well 
neither does the SAT. Because RCT runs on fast and powerful laptops, 
RCT is quite capable of sampling 88 notes to create a tuning. You may 
be excited to learn that Dean and I plan on adding 88-note sampling 
to RCT some day.
   But sooner than that, we hope to add two to six notes to RCT's 
existing six-note sample set, most likely the notes immediately above and 
below 
the bass-treble break, the notes immediately above and below the 
wound/unwound 
break, and perhaps a few notes in the lower temperament (F3?) so as to 
precisely 
predict the beat speeds of 3rds (e.g., F3-A3). 

>The biggest job of the Beta testers
>was to help come to some unanimity as to the best "middle of the road" type
>of tuning which was assigned to the #4 OTS. 

  Not quite. The dozen or so beta testers offered lots of input on how to 
get RCT to truly
reflect our various aural and mathematical proclivities. Some of us favor 
OTS 4, 
some prefer OTS 7 or 3, but most of us use different OTSes in different 
situations. 
    The beta testers' biggest job was to help verify that OTS and Custom 
EQ algorithms 
were flexible enough to create aural-quality tunings no matter the OTS or 
piano scale. 
During the two years (wow time flies!) of RCT's existence, beta testers 
and 
RCT users have come up with many lots of great ideas, including James 
Grebe's 
suggestion to show A4's actual pitch in beats *and* cents so you know 
immediately
if you'll be fine-tuning or pitch-raising, Carl Lieberman's suggestions 
about the 
limiting stretch in the high treble on poorly scaled pianos, Michael 
Travis's suggestions 
for streamlining recording of an aural tuning (e.g., Examinee) in 12 
minutes or less, 
Kent Swafford's great insight on just about everything, etc.

   Jim writes that he prefers the SAT in part because

>It utilizes tuning by the same partials as the previous SATs. It
>has the same familiar display.

   I prefer RCT because it breaks new and fertile ground.

Mitch Kiel



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mitch Kiel, RPT
authorized Reyburn CyberTuner sales and support
1-888-I-LUV-RCT (1-888-458-8728)

11326 Patsy Drive SE    
Olympia, Washington 98501 USA
email: mitchkiel@olywa.net
Visit the RCT Web site at www.reyburn.com