adaptive tunings

The thread between Jeff Lofflink and POL:

******

> I'm open to any ideas on this. I got the idea from the Justonic
> folks. I use new note only updates myself. They were more inclined
> to real-time updates, giving as an example barbershop quartets where
> a pitch swoop wouldn't be out of place. The MIDI Tuning standard
> also requests real-time updates. Do we really need both types
> available simultaneously?

Pass. Is Bill (Sethares) on the list these days? any feelings on
this? Neither is something I use at all, currently, but the option
would be hugely advantageous, and I'm sure I would were it
convenient. Two major problems are (a) defining the logic (b)
making that logic configurable. One thought: personally, I think I
would be more or less content if this could be implemented as a
convenient 'post-production' technique. But people who are
interested in using these machines for live performance would
presumably want more than this?

******

I think its fair to say that there's a real "chicken and egg" problem
with adaptive tunings. It's hard to compose or perform with adaptive
tunings because there's no nice implementation - and there's no nice
implementation because no-one is composing/performing that way.

I went to Ensoniq and gave a presentation about various tuning
issues, with a heavy emphasis on adaptive tunings, and they thought
it was all very interesting, and thank you for coming. Given that their
tuning expert (Steve Curtain) has moved on to other places, I don't
they're a likely source for something like this at the current time
(though I'd love to be proven wrong).

All of my adative tuning work has been "off-line". I make a standard
MIDI file, read it into my adaptive algorithm, wait a while, and then
check out how it did. This is a very awkward way to work, and is
essentially a kind of 'post-production' method as you describe. I
think adaptive tunings will only be really useful when you can sit
down and play as if it were a musical instrument. Such 'post-
production' methods are fine for demonstrating the concepts, but not
for exploring the technique fully.

I'm currently attempting a 'real-time' version using Max, though its
unclear at the present time how many simplifications are going to be
needed before it will actually run in real time. Of course, this is for
MIDI instruments only. A far more interesting thought is the idea of
operating on acoustic sounds...

Bill Sethares

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End of TUNING Digest 1459
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Carl Lumma wrote:
> My question is: Does anybody know how the basilar membrane works? I
> thought that a given spot on it was sensitive to a particular frequency

That's the ol' Helmholzian "place" theory. There have been more
recent studies that suggest that lower frequencies are perceived very
differently from higher ones.

I certainly don't claim to be an expert on the topic though. Brian
McLaren has surveyed a LOT of recent literature on the topic.

> Date: Sun, 28 Jun 1998 01:44:54 -0700
> From: Carl Lumma

> My question is: Does anybody know how the basilar membrane works? I
> thought that a given spot on it was sensitive to a particular
> frequency, and that these spots were arranged in order of decending
> frequency along its length. Now what stumps me is how a given
> frequency only vibrates an isolated part of the membrane.

You're right, a point on the BM can't respond to only a single
frequency. Instead each point acts like a bandpass filter.
Excitation causes a travelling wave to move down the BM, and
different frequency components of the wave peak at different places
as it progresses. The portion of the BM nearest the middle ear is
stiffest and responds best to high frequencies, and the membrane
becomes increasingly floppy along its length, lowering the "best
frequency" of the bandpass filters.

For some nice animations see:
http://www.neurophys.wisc.edu/animations/

or download the whole "Auditory tour" (20MB):
http://www.neurophys.wisc.edu/ftp/pub/aud-tour/
--
Ewan Macpherson
Central Systems Laboratory
Kresge Hearing Research Institute
http://www-personal.umich.edu/~emacpher

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End of TUNING Digest 1461
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In a response to my post, Carl(I think) questioned my claim that the
resonance of different areas of the basilar membrane was due to variation
in width. He mentioned the fact that it is also due to variations in
stiffness.

i reply that variations in width and stiffness are not mutually exclusive.

-Jesse