DAC and real musical instruments

[Martin Czech]

:::I don't think so. Not in any real world situations. At  least our piano isn't 
that accurate right now. And even if we have it tuned, how long will it stay 
that accurate?
:::The Hammons organ uses a fixed division ratio that introduces errors. I don't 
remember the integers, I suppose somebody else can fill us in. The exact errors 
should be simple to calculate.
:::The intonation of the violin and clarinet is dependent on the skill of the 
player. Maybe a really good player can achieve 0.5% to 0.3% error on a good day? 
Or maybe not.
:::And in any case, the entire tempered scale is a compromise. So very high 
accuracy is rather pointless. Some intervals sound less than perfect even if 
they are theoretically totally in tune. An remember that pianos are 
stretch-tuned, so they deviate from the true scale on purpose.


Note that the whole subject is most important for unisono lines,
requirements for accuracy are less for far away notes, of course, because
they can't cancel to 0.  So if the application is to play allong with
some digital instrument in unisono lines, accuracy is demanding.

I think it is all about beating or beat frequency, forget the absolute
frequency values. Deep beating causes a tremolo , if this is faster then
, say, 2 Hz it starts to get unpleasant. This would be the case for 440
and 442 Hz, ie. 0.4% deviation. The higher, the worse.  Remember that
acoustic instruments (or those who are electric or electronic but are
acoustically played and recorded) will never have such a deep beating
like several electronic sources mixed by electronic means. This makes
unintended electronic beat frequencys so extremely unpleasant.


This leads to another question: How can we avoid the "electronic"
beating, say for string sounds, if it is unintended? I think that the
direct recording without any reflections or reverb is the main cause for
"sterile" electronic sound (bad word). I tryed to use stereo spread,
ie. the different voices get different pan values, so they can't cancel
exactly. It is interesting to note that the way we apply reverb will
of course not be helpfull, because we do it AFTER electronic mixing
of the sources. Avoiding cancelation effects would mean to provide
extra and slightly different reverb settings for each unisono voice,
i.e. before mixing.


btw.: My Carvin guitar has not been tuned for several months (!), and
it has a Floyd-Rose type vibrato, which is known to impose stress on
the strings. Still, even the higher strings are perfectly in tune, the
beating is slower then 1Hz or so. This makes the 0.3% figure sound very
realistic. Good mechanical instruments can be very stable, provided that
room temperature is quite stable (which is the case in my living room). A
tuning fork was the time normal (sp?) ages before quartz clocks came.
And think of precision tuning fork resonant frequency measurement
things, that were once used in power plants etc.

I still have a crap Corean guitar with disastrous stability. In case
of extreme distortion (which is my prefered  mode) beating can lead to
allmost perfect cancelation (which is an exeption to what I said earlier
about mechanical beating) which is also very unpleasant for octave lines
or chrunchy cords. So, mechanical instruments can be crap, too.

m.c.