[Chris Whealy]

James wrote:

I just found that adding a 3rd horn to the unison line seems to help
quite a bit. Apparently it somehow masks or breaks up the phasing
effect.

Congratulations! You've just discovered the secret behind why a
"section" of instruments is never a "pair".

If any two instruments play the same part, they will /always/ sound bad
together. Its like death and taxes - its just one of those facts of life.
In your case, you describe the badness as being phasey, but nonetheless
you'll hear similarly unpleasant effects if you had a pair of violins or
clarinets or cellos.

This is because the ear is very sensitive to small pitch differences in
a pair of similar signals. The brain's perception of these differences
can be reduced by adding a third (and preferably a fourth) copy of the
signal. Now the brain cannot determine the difference between a pair of
these signals, because it is masked by the presence of the third signal.

Now add a fourth version of the signal and the brain will find it
totally impossible to distinguish the mismatched pair it heard at
first. Instead, it will simply perceive the overall average pitch - and
this is the sound we get from a section of instruments. If you add a
fourth copy of your trumpet line, you'll hear a real horn section sound.

I have exactly this problem at my church where we have two violins and a
cello. I have had to specifically ask the music arranger not to score
the two violins on the same part, but instead, give them separate
harmony lines. Even though they're both good violinists, if they play
the same part together, it sounds like the proverbial neighbour's cat on
the back fence serenading the ladies at 3AM....

Chris W

--
The voice of ignorance speaks loud and long,
But the words of the wise are quiet and few.
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