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Courses on sound synthesis with maxmsp patches (idea, feedback, question)

July 31, 2006 | 3:33 pm

Hi :)

First post here, i’ve recognize some quite famous persons here !

Anyway, i will present a short course on sound synthesis (my hobbie) in paris.
I ve decided to present different sound synthesis according to J.O SMith classification

I ve implemented simple maxmsp patches with temporal and spectral representation for each synthesis (patches are made for pedagogical issue, the goal is not to create incredible soundscape :) ). You can download patches here:

http://vincent.choqueuse.free.fr/MAXMSP/secret.htm

Does anyone have some critism about the patches ? Some idea to make patches more adapted for educational issue ?

Then, I ve a problem with my additive patch. In fact i would like to show how to obtain square, swatooth and traingle wavform by summing 6 sines (In fact this waveform need to have an infinite harmonics, but with matlab i ve verified that 6 sines can give good apporximation).

My problem is: " when i look to the oscilloscope, i don’t obtain the correct waveform".

I believe that there are some phase problems ? How to synchronise the phase of each sine ?

Some idea ?

thank’s !


July 31, 2006 | 4:28 pm

Quote: Choc wrote on Mon, 31 July 2006 09:33
—————————————————-
> My problem is: " when i look to the oscilloscope, i don’t obtain the correct waveform".
>
> I believe that there are some phase problems ? How to synchronise the phase of each sine ?
>
> Some idea ?
>
> thank’s !
—————————————————-

i’ve not had time to look at your patches, but the answer to your question is to use a phasor to drive your cycle oscillators via the second inlet (phase inlet).

j


July 31, 2006 | 5:21 pm

> My problem is: " when i look to the oscilloscope, i don’t obtain
> the correct waveform".

keep in mind, that summing sine waves (not cosines) will give you the
typical rectangular waveform.
use the right inlet of cycle~ to set the initial phases of your
partials to something like 0.75 or -0.25.


July 31, 2006 | 6:19 pm

Also, get info on scope~ and change it from line~ (or free-run) mode to
"up" mode. This will make the oscilloscope phase synchronous.

Peter McCulloch

On Jul 31, 2006, at 1:21 PM, vb wrote:

>> My problem is: " when i look to the oscilloscope, i don’t obtain the
>> correct waveform".
>
> keep in mind, that summing sine waves (not cosines) will give you the
> typical rectangular waveform.
> use the right inlet of cycle~ to set the initial phases of your
> partials to something like 0.75 or -0.25.
>
>


July 31, 2006 | 8:42 pm

On 31-Jul-2006, at 17:33, Choqueuse wrote:

> My problem is: " when i look to the oscilloscope, i don’t obtain
> the correct waveform".

I did exactly this in a workshop last week. And, yes, the waveform is
not what you expect. And, yes, it’s the phase. The standard Fourier
models for square wave & Cie. use sine waves; cycle~ produces a
cosine wave.

The thing is, the ear tends to be less sensitive to phase offsets in
static wave forms, so the difference is more striking visually than
acoustically.

Nevertheless, if you want things to look right, you’ll need to send a
phase offset into the right inlet of your cycle~s before starting
audio. I think 0.25 will do the trick.

Good luck,
Peter

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July 31, 2006 | 9:18 pm

Thank’s a lot everybody for your advices

I’ve just use what you told me…
By appling a phase offset of 0.25, i obtain a sine wave

cos(x+0.0.25*2*pi)=cos(x+pi/2)=sin(x)

Then the fourier decomposition works well !

Don’t hesitate to look to my other patches. there are some patches for waveguide (karplus strong), waveshaping, granular, FM, and subtractive synthesis


July 31, 2006 | 10:14 pm

I enjoyed these patches a lot, very curious in what educational way they are used, you are giving a small course, can you tell a bit more about a that?

Anyway, nice and keep up the good work!


July 31, 2006 | 10:29 pm

I will make a small presentation on sound synthesis (1H or 2 H) in Paris for "Le salon de la musique et du son"

I will explain how different sound synthesis work:
- sSignal models (additive,subtractive)
- Abstract algorithm (FM, waveshaping)
- Physical models (Waveguide)
- sampling & Granular.

i explain how this sound synthesis work in a powerpoint presentation and to illustrate it, i present patches on maxmsp with frequency and time representation, etc. I hope it will help people to understand the bases of different kind of sound synthesis.


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