Klarinet Archive - Posting 000088.txt from 2004/09

From: Tony Pay <tony.p@-----.org>
Subj: Re: [kl] Stretch octaves (1)
Date: Sat, 4 Sep 2004 14:42:01 -0400

On 4 Sep, I wrote:

> I think that the notion of 'stretch' octaves on the piano isn't
> particularly well understood, in general. I remember misexplaining it here
> -- though I did correct myself later:
>
> http://test.woodwind.org/Databases/Klarinet/2000/08/000543.txt
>
> Would you, Dave, be willing to make a post explaining why stretch octaves
> are necessary on the piano, and how we need to understand them in order to
> play acceptably in tune ourselves?

What Dave subsequently posted is quite right. However, it assumes more
knowledge than I think many Klarinet subscribers will have, and I'd like to
fill in the gaps.

The first thing we need to understand is the difference between instruments
like the clarinet, that are continuously driven by energy input as they're
played; and instruments like the piano, that receive an initial energy input
via the impetus of the hammer on the string, and then resonate as the sound
decays.

It can be demonstrated that the difference between these two sorts of
instrument is basic.

Instruments like the clarinet have sounds that are called in the literature,
'harmonic'. That means that when you analyse the sound spectrum of a
clarinet, you find it consists of a fundamental, plus overtones that are
whole number multiples of that fundamental.

But on the other hand, you can't really analyse the sound spectrum of a piano
in the same way. The best you can do is to say that it consists of a
fundamental and a collection of overtones -- but those overtones are only
more or less multiples of the fundamental.

It's worthwhile sitting with this situation for a bit. Why would it matter
that the overtones are, or aren't, multiples of the fundamental?

Well, the reason is to do with how our ear/brain systems assign pitch. When
I said above, "when you analyse the sound spectrum of a clarinet", I didn't
just mean, analyse it *mathematically* -- although you can do that.

I meant that that's how our ear/brain systems do it. And when our ear/brain
systems have to analyse the sound of a piano, they do their best: but on the
same model as they use to analyse the sound of the clarinet.

So, why do our ear/brain systems regard the model of instruments that are
continuously driven -- like the clarinet -- as more basic than the model of
instruments that are initially excited and then allowed to decay?

Well, we don't *really* know -- but we can make a good guess. It's because
the shrieks, yowls, growls, animal calls -- all the sounds of the jungle --
were extremely important to us as we evolved. We needed to hear, locate and
identify them in order to survive. And notice, they were all sustained, and
continuously driven.

We needed to be able to perceive what's just 'a collection of frequencies' as
-- an entity.

Just imagine if we hadn't been able to do that. We wouldn't have been able
to recognise 'a tiger', for example.

Pianos, and percussion instruments, just weren't in on the act. The way we
analyse their sounds is just as approximations to what was fundamentally
important to us.

(To be continued.)

Tony
--
_________ Tony Pay
|ony:-) 79 Southmoor Rd tony.p@-----.org
| |ay Oxford OX2 6RE http://classicalplus.gmn.com/artists
tel/fax 01865 553339

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