Re: Pitch orientation-discriminating feature detectors?

[Martin Braun <nombraun@xxxxxxxxxxxxxxx>]

Daniel Pressnitzer wrote:

> The next question is of course why would it be useful in the real
> world to process differently upward vs. downward frequency
> movements...

Thanks, Daniel, for introducing this question to the thread. It's a highly
interesting one.

Before coming to the biological background, let me start with a short
musical introduction. For some strange reasons, frequency sweeps had been
banned almost totally from classical European music. This has changed in
recent decades, and people like Yannis Xenakis have written most fascinating
pieces where frequency sweeps (musicians call them glissandi) are quite
dominant. In other musical cultures these techniques have a much longer
tradition, like in Japanese flute und string music.

Several years ago I did some engineering on musical wind instruments that
can produce slides. The only wind instrument in classical European music
which can do this is the trombone. So I developed, and let build, a slide
flute in the same size as the common concert flute. After that I also
developed a slide bassoon.

Recently I saw, and heard, in a professional Swedish Jazz band a guitar-like
zither that was plucked with one hand while sliding a steel hand over the
strings with the other hand. A most sophisticated instrument. Nothing like
the old Hawaii guitar.

In short, I have some experience how frequency sweeps sound like. The
difference between rising and falling pitch sweeps is striking. Upwards
raises tension, even alarm. Downwards evokes relaxation.

Now to the biology. In the vocalization of probably all mammals we have more
slides than steady states. Upslide is associated with an increased lung
pressure, and downslide with a decreased one. Further, increased lung
pressure and upslides are associated with the animal's excitation, the
reverse with its relaxation. Therefore the former is a sign of alarm, the
latter a sign of calm.

Perhaps we should also remember our police car and air raid signals. The
terrifying parts are the upslides.

No wonder at all, that there are plenty of neurons that respond
direction-specific to frequency modulation.

Martin

-------------------------------------------
Martin Braun
Neuroscience of Music
S-671 95 Klässbol
Sweden
e-mail: nombraun@post.netlink.se
web site: http://hem.netlink.se/~sbe29751/home.htm