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From: rlr@pyuxd.UUCP (Rich Rosen)
Newsgroups: net.music.synth
Subject: Re: Instrument Harmonics wanted
Message-ID: <2452@pyuxd.UUCP>
Date: Sat, 25-Jan-86 22:50:45 EST
Article-I.D.: pyuxd.2452
Posted: Sat Jan 25 22:50:45 1986
Date-Received: Sun, 26-Jan-86 16:54:01 EST
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> Re:harmonics wanted--
> You want what everyone wants and for sure exists but doesn't seem to be
> published anywhere: a complete set of data for the harmonic (or inharmonic)
> spectra of all of the common acoustical musical instruments.  The problem
> seems to be that there is an enormous amount of data to deal with. 
> Wendy Carlos discussed this problem and her solution in working with the
> Crumar Synthesizer (an additive synthesis machine) in a recent issue of
> Keyboard (unfortunately, I can't find my copy).

Not to shatter anyone's bubble, but it turns out real accurate reproductive
music synthesis is not dependent on just knowing a fixed set of harmonic
spectra for specific instruments.  Envelope is probably at least as important
as harmonic content (if not more so) in recognition of specific sounds.
The harmonic spectrum (AND the envelope) often change drastically over the
range of an instrument.  For instance, the piano, which has a slightly
inharmonic spectrum, is deliberately tuned such that octaves are "stretched"
to give it its characteristic sound.  (The specifics of piano tuning are
a bit beyond my understanding, so if someone thinks it necessary to expand
upon and correct my simplified summary, please do so.)

Plus harmonic content changes very drastically over the course of a note.
(This is supposed to be one of the plusses of FM synthesis.  The way in which
envelope control of modulation index affects changes in frequency spectrum
makes for some interesting sounds.)  In addition, inflection and intonation
cause subtle changes in overall sound.  One thing I've found from playing
with the sax sample on my Mirage is that it sounds awful if you don't
play it right.  Played straight it sounds like a cheap organ.  Played with
a little inflection (the note that begins each passage started at just above
the actual pitch of the note quickly bending back into pitch, plus slow
variable introduction of vibrato on held notes) adds a lot of believability
to the sound.

I would think that precise accuracy in harmonic spectra for many instrument
simulations is actually less important than many of these other factors,
though in fact part of the reason an instrument like the piano is so hard
to reproduce is its slight inharmonicity that defines its sound.  I've
been told some of the hardware in the Kurzweil is specifically devoted to
idiosyncrasies of the piano and is in fact unavailable for other user
defined sampling reproductions.
-- 
Life is complex.  It has real and imaginary parts.
					Rich Rosen  ihnp4!pyuxd!rlr