Peterson AutoStrobe 490 - Manual (Page 12)

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return the screen to the SETUP menu. The power-up condition of the Model 490 will now reflect these latest parameter
settings until new values are once again stored under SETUP.
c) VIEWING AND ALTERING TEMPERAMENT FILES
Temperament refers to the specific frequency (pitch) intervals placed between notes in a musical scale. With 12 notes per
octave (the most prevalent case but, by no means, the only case), there are an infinite number of ways to set the audio
frequencies of these notes relative to one another. Through the centuries, many have wrestled with the challenge of creating
the most pleasing, yet universally flexible, temperament of these 12 intervals. It turns out that it is mathematically impossible
to achieve both completely, that is, if by "pleasing", one means smooth beat-free intervals, and, if by "flexible", one means
satisfactory harmony in all possible key signatures.
The AutoStrobe 490 always powers up with Equal Temperament and all offsets applied to notes when defining (editing)
custom temperaments are relative to it. In other words, if one creates a temperament in which the C# note is 5.2 cents sharp
from the pitch for C# in an equal-tempered scale, a setting of +05.2¢ would be entered. Since the overall frequency standard
(both internationally and for the Model 490) is "Concert A", it is suggested that custom temperaments be created with the
"A" scale note maintained at 00.0¢ offset and then adjusting the other scale notes appropriately. In this way, the "A=xxx"
setting under the SETUP menu will still be physically accurate.
The Model 490 comes with 8 non-erasable, unmodifiable temperaments including standard equal temperament. They vary
considerably in the "pleasing versus flexible" compromise that all temperaments must address. All unequal temperaments
use "C" as the home key. Those familiar with published temperaments will recognize most of these eight temperaments as
both historically and musically useful:
T490 NAME FULL NAME DESCRIPTION
EQUA EQUAL All semi-tone intervals are identical: 12 / 2 or .6% above previous
note. All keys signatures are equally playable.
PYTH PYTHAGOREAN Perfect 4ths and 5ths; 3rds are poor. Avoid G< major and minor
keys. F<, C< major and E=, B= minor diatonic keys are very good.
JUMA JUST (MAJOR) Perfect triads in 12 keys: C, G, A, E, E=, F major and A, E, F<, C<,
C, G minor. Avoid all other keys.
P5TH POWER FIFTHS Tempered for clean 5ths when playing electric guitar with distortion.
MEAN QUARTER COMMA
MEAN-TONE Perfect/excellent triads in 16 keys. Avoid D=, G=, A=, B major and
B=, E=, F, G< minor keys.
WRK3 WERCKMEISTER—III Well-tempered; strong differentiation of key color. Avoid D=, G=,
A=, B major and B=, E=, F minor keys.
KRN3 KIRNBERGER—III Similar to WRK3 but also avoid E=, E major and C, C<, G< minor
keys.
YONG YOUNG Mild differentiation of key color. Avoid D=, E=, G=, A= major and
B=, C, E=, F minor keys.
Although they cannot be edited directly, one may always copy any one of these permanent temperaments into a custom
temperament which can then be viewed or edited further on a note-by-note basis. The Model 490 permits up to 64 user-
programmable temperaments which can be created in this way or "from scratch".