[sdiy] ASM-1 VCO questions--it works!!!!

[Magnus Danielson]

From: Andre Majorel <amajorel at teaser.fr>
Subject: Re: [sdiy] ASM-1 VCO questions--it works!!!!
Date: Mon, 24 Mar 2003 14:13:24 +0100

Bonjour Andre!

Ca va?

> On 2003-03-24 00:11 +0100, Magnus Danielson wrote:
> > From: Andre Majorel <amajorel at teaser.fr>
> > Subject: Re: [sdiy] ASM-1 VCO questions--it works!!!!
> > Date: Sun, 23 Mar 2003 22:25:12 +0100
> > 
> > > On 2003-03-23 21:01 +0100, Magnus Danielson wrote:
> > > 
> > > > Bon soir Harry,
> > > 
> > > Bonsoir (it's one word).
> > 
> > Oh... it's over 15 years since I had my last French lesson, so I think
> > a little slip in the spelling is to be accepted, now is it? ;)
> 
> Ha ! Let me make this perfectly clear : given the state of my
> Swedish, I wouldn't *dream* of criticising your French. :-)

We've got a deal! ;O)

> > ... but I thought I bored the hell out of people with my formulas...
> 
> They're a bit hard to follow sometimes, but this is not
> rec.humor.jokes or rec.writing.cliffhangers.

Right. I do them to show that the magic behind the scenes really isn't THAT
complex as some people think. By showing it people might forge similar things
themselfs and probably get away with it ;O)

If it's humor, it's at least a higher level of meta-humor ;O)

> > > The drum synthesis demo is at
> > > 
> > >   http://www.teaser.fr/~amajorel/misc/dr.mp3
> > > 
> > > It would probably make a real drummer laugh, but I feel it's not
> > > bad for a 300-line program that was hacked together in an hour
> > > or two.
> > 
> > No, not bad under the conditions... but one of the things that annoyed
> > me with that discussion where:
> > 
> > 1) The loss of the modes where not given, but I know they vary. The
> >    loss of the modes translates into the speed of decay.
> 
> In this sample, the decay rate is proportional to the square of
> the frequency. I've read it's the general tendency in natural
> sounds. The actual relationship is probably more complex.

I've got a borrowed book which very clearly states otherwise!

I have not (yeat) stretch my mind around the full aspects of Bessel-solutions
for this case, but I take it as a good reason to learn more about this white
spot on my map.

> > 2) When you hit a drum you will not induce equalently amount of energy
> >    into the modes. The energy-insertion depends on position and size
> >    of the drumstick.
> 
> True. If you hit a node, I don't think the corresponding partial
> will ring. As guitarists know.

In a sense yes, but in the string case things are simple since they are in 1D
where as this is a 2D thing, so any of the waveforms which is non-fundamental in
the angular dimension will have it's node "phase" on the drum-skin adjusted by
the position you hit, i.e. they have a fixed radial position but will adapt the
angular position according to hit-position. This property is maybe one of the
more confusing ones, but when you think of it, it will come as naturall as you
think of what makes the basis for each dimension.

But you also have to consider high-frequency patterns, where a big object will
induce both on positive and negative fields, which will then cancel much of the
energy actually initiated and thus will that mode be weaker than if a harder and
smaller object had hit the same position.

You can do alot of coloring of the sound my just hitting in different places.
Naturally, if your a bad drummer you hit all over the places and it doesn't
sound the same way. Good drummers naturally use this coloring for good emphasis.

> > 3) Dampingmaterial on the drumskin (the soft hand damping for
> >    instance) will effect the loss of modes, and is also positinally
> >    and size dependable.
> 
> And shell resonance, bottom skin, etc.

Yeap.

> What I like least about the simulation is the attack. I suspect
> that a short burst of noise is needed.

But some of the modes would die almost directly, which makes the attack so very
much more interestingly sonically.

Cheers,
Magnus