4 lights

[Jim Coleman, Sr.]

Hi JimRPT and all other interested parties.

I lifted a quote from one of your recent Pearls of Wisdom.

"  Anyway I am actually trying to find a way to ask Dr. Coleman about 
his "four
light" tuning comment and thought that jumping in on this thread might 
give me
an opening............oh well, mice and men :-)
Jim Bryant (FL)
"its the unisions Jim, the unisions"
WJ Kelly, IPT, OHOAGU"

Let me answer the last first. Actually, unisons are first in importance,
last in accomplishing and always most noticeable. They can even be done
with an ETD from the midrange on up (not the Bass, too many variables).
This brings me to the first topic above. 4 lights. There are times when
you will notice that 4 and somtimes 5 lights are lit at the same time.
This is good, because it shows greater accuracy potential. The 
significance of the 5th or center light is only for the purpose of showing
which direction the lights were last moving (ie, in the sharp direction).

When the LEDs move from one position to the next (one half revolution
is equivalent to 1 HZ change) in one second, this represents 1/4 beat per
second (bps) variation from what is called for. Just as the next position
is realized, there is a brief moment in which we have what I like to call
the fence-riding position. During this moment, one can see that the next
pair of LEDs is getting brighter while the last pair are getting dimmer.
When the last pair are dark, this represents 1/4 bps change in pitch. If
you can tune very carefully just before the last pair of lights go out, you
can achieve a rare degree of accuracy. Just think with me for a moment. If
you can hold 4 lights on for 2 seconds your accuracy goes to within 1/8
bps. If you can hold 4 lights on for 4 seconds, you have 1/16 bps accuracy.
If you can stop 4 lights dead on so that there is no movement, (neither
pair of lights is getting brighter or dimmer) the accuracy is almost infinite.

Did you see those big IFs above? It requires special techniques to approach
this kind of accuracy. A piano tone is transient (ie changing during its
duration, to be redundant). One must develop a rhythm of tuning loudly and
testing softly. Playing softly samples a more even part of the decay curve
where there is less pitch variation. The touch weight must be quite 
consistent and the moment of decision relative to the decay curve must be
consistent. Since Dean has inaugurated the targetting blossum or bloom, the
users of RCT are finding it quite difficult to keep the full blush on 
for any length of time using the default spinner setting. Keeping the 
partial blush on consistently is not easy either. This is analogous to the 
4 lights on the SAT. Keeping them on is one thing, keeping them stopped is quite
another thing. Dr. Sanderson invented the 4 lights phenomenon over 20 years
ago, some of us slow learners are just catching on to it.

There is no question as to the practical accuracy of either
machine. Once Steve Fairchild asked Dr. Sanderson if he could add a second
digit to the cents readout on the SAT. Steve computes his Aural Tuning 
Emulator using 6 decimals, but he no longer has any interest in increasing
the readouts on the SAT (I asked him). Our problem is not the number of 
readout digits, but it IS in tuning to the accuracy of one digit, forget 
2 or 3 digits. The difficulty of achieving stillness of the rotation far 
outweighs the 2nd or 3rd digit. I would encourage all who use ETDs to strive 
for the ultimate in stabilizing the rotation using the blush or the 4 lights.

Jim Coleman, Sr.