Klarinet Archive - Posting 000416.txt from 2001/02

From: Bilwright@-----.net (William Wright)
Subj: Re: [kl] Re: strange intonation in warm up exercise
Date: Sun, 11 Feb 2001 23:02:21 -0500

<><> Tom Labadorf wrote:
When you have two pitches sounding closely in tune, the nodes will align
at regular intervals

I don't want to offend by beating this topic to death, Tom, but
here's one final example:

Suppose the graph of a sound wave has three different peaks. How
are you going to decide _from the graph alone_ whether the peaks
represent three different instruments which are playing three different
pitches?
Or could the graph represent two instruments playing different
pitches that happen to produce a difference tone? Or could it be a
single instrument playing a fundamental tone with two overtones?

How would you decide?

The only answer to this question is to compare some other
quality(ies) of the three peaks. For example, does the lowest pitch
equal the difference between the two higher pitches? Even if the
answer to this question is 'yes', how can you be sure that three
musicians aren't playing these particular pitches just to fool you?

....well, if the *amplitudes* of each peak have the correct
relationship for a difference tone, you would be more certain. But the
question _still_ remains: Can you be absolutely sure?
Your next test may be whether three pitches are related to each
other as harmonics. If they don't have a harmonic relationship (small
integers), then something is wrong. Or perhaps each peak has an
asymmetry that matches the other two. And so forth....

My point is: Whatever quality(ies) you choose, you are doing the
same sort of thing consciously that your nervous system does
unconsciously. You are selecting a particular detail(s) of the curve.
There's nothing wrong with this, but the fact is that you are adding an
interpretation to the graph that is not in the graph itself. You are
saying, "I will call this a difference tone because....."
Will your tuner measure the same details as you did (consciously or
unconsciously)? Will the tuner's computer chip arrive at the same
decision as you did?

I don't know enough about electronics to know how a tuner works.
I'm just trying to point out that 'difference tone' is an interpretation
and not a physical necessity. Even if you could see that two
clarinetists were playing, and yet you could hear three tones, you could
not be absolutely certain <here comes the conspiracy theory> that
someone wasn't hiding behind the curtain and playing a third tone.

Cheers,
Bill

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