The concept of "physical modelling," the fact that the material structure of
the medium (pipe), producing a sound, determines its timber and its length
determines its pitch, or the frequency of that timber, is somewhat confused
by the factor of scaling. Seemingly, the "recipe" of harmonics and
amplitudes for any given timber applies to any frequency (note or Midi Key
number). That is,
an Oboe wave file, synthesized using harmonic amplitudes, produces an Oboe
timber at any frequency. If, for example, one synthesizes additively by
varying the amplitudes of component sine frequencies, beginning with 8'-C,
4'-C, 2-2/3'-G, 2'-C, 1-3/5'-E, 1-1'3'-G and 1'-C, the computer has the
ability to transpose the resulting timber for each of the frequencies of
pitches of the keyboard. The notion that the timber of 4'-C of a Principal
stop is physically-modelled using the recipe of harmonic amplitudes for D#,
it seems to me, is one of "same difference." The proposition becomes that,
"frequency varies timber." I think this is deceptive, since it is provable
that timber remains the same because of its constituent properties, just as
frequency is fixed.
Years ago, when I first analyzed some of the General Midi Soundfonts which
were professionally produced, I was struck by the fact that many of the wind
instruments used an Oboe for the upper registers, the highest treble notes
of the compass of the instrument. The distinction of timber was not
detected at those frequencies. One might as well say that "above 2048 Hz,
all timber in woodwinds is flute tone." This is disputable, of course. I
don't believe the same can be said of the factor of scaling with respect to
timber. While there may be truth to the fact that bass notes need more
harmonics to sound realistic, why would the recipe of those harmonics change
with frequency, if and since frequency (pitch) is, factually, determined by
the length of the material medium (pipe) and timber were (hypothetically)
determined by particular structure and scale?
Rameau's "Treatise on Harmony" deals with the specifics of frequency derived
from the length of a string. While there may be 4 or more different
qualities of materials used for strings, determining their timber, the
concept of "fretting" strings to shorten their length to produce a given
pitch or frequency does not change the material (constituent) structure of
the string. So I believe that the "recipe" of harmonic amplitudes for a
given instrument or organ stop is a valid concept. Transposition changes,
incrementally, the frequency of the ensemble of harmonic upper partials at
the specified amplitudes which determine timber. This is what must be
constant and consistent throughout the compass so that it is identifiable
(psycho-acoustically) as an Oboe, for example.
Perhaps, I don't yet understand the science that is presented with respect
to "scaling," as it relates to the maintenance of timber. It almost seems
to be a denial of the consistency of theory with respect to the recipe for
harmonic amplitudes which determine timber, based on the idea that
frequency, determined by length, somehow distorts timber. Is this a
correct perception?
John Beach
-----Original Message-----
From: John Reimer
Sent: Tuesday, June 13, 2017 5:14 PM
To: jorgan-***@lists.sourceforge.net
Subject: Re: [jOrgan-user] Trendline Synthesis
Post by Thomas BeckFor those of you who are interested in synthesizing pipe sounds, here is a
link to an article by Colin Pykett about a new technique called trendline
synthesis.
Tom,
Thank you for drawing our attention to this very recent article of Colin
Pykett’s, which is a development of an earlier one (but also quite recent).
Colin’s website has long been a marvelous source of information and sanity
about all types of pipe organs and pipe organ substitutes. I was fascinated
to read the earlier one, as I realised that I had been using his trendlines
for many years (without using that term) in my attempts to classify organ
sounds, all based on harmonic analysis of actual recordings. It was second
nature to use logarithmic graph paper because of my engineering background.
I was plotting straight lines indeed!
What Colin is proposing in his latest article could be of great use to those
of us who want to explore the possibilities open to us in tonal synthesis.
When I first became involved in jOrgan some years ago, synthesis was the
only real course open to many of us, but now that developments in computer
resources has gone ahead in the way it has, I have no personal interest in
synthetic sounds any more, because of the musical satisfaction to be gained
(by me, at least) by using well-produced recorded samples. Having said that,
I was pleased to see the common sense being shown by Colin in the article,
in questioning what he obviously regards as undue complication in some
programs which offer high quality pipe organ simulation, and which imply
that this sort of extra complication is really necessary. Of course, there
will always be some organists who really do want those extra complications,
and I say - if they are happy to go those lengths - by all means pursue
them.
John Reimer
--
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http://jorgan.999862.n4.nabble.com/Trendline-Synthesis-tp4665134p4665138.html
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