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 Forum index » DIY Hardware and Software » Les Hall's Projects including eChucK
The Physical Modeling eChucK DIY Project
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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 5978
Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Mon Mar 22, 2010 10:38 pm    Post subject: The Physical Modeling eChucK DIY Project
Subject description: Converting computer models into analog form
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After thinking about the concept for a while, I realized that the same techniques I have used to implement the Karplus Strong algorithm as an analog circuit can be applied to many physical models of musical instruments. I see this as an emerging category in the modular synthesis category: physical instrument models.

For example, what if a modular synthesizer owner could just patch in a flute model and have a flute in the performance. Or a Trombone or a woodwind, etc. It's already done with drum machines and perhaps other instrument models and earlier pioneers in modular synthesis have performed exactly this stunt by wiring up modules. The next step, i feel, is to offer specialized circuit boards that perform like real instruments, or at least like models of real instruments.

The technique that I've been working with is simple. First I make a ChucK software model of the proposed circuit, being careful to use only analog hardware implementable programming constructs. This includes delay lines, multipliers, VCOs, VCFs, summing and difference amps, etc. Then once the software model is complete I convert it to a circuit board schematic, breadboard that, then have circuit boards made. The result will hopefully become a new line of modular synthesis products.

Attached you will find my first wind instrument ChucK model, the blown pipe model. Both source code and audio test file are attached. I plan to develop additional software models in this fashion and select one for the first design. Please feel free to modify the software models, change parameters, and generally play around with them. I encourage you to post any comments or suggestions you may have.

Les


Blown Pipe Demo 2 20100323 0124.mp3
 Description:
Blown Pipe Demo 2

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 Filename:  Blown Pipe Demo 2 20100323 0124.mp3
 Filesize:  802.04 KB
 Downloaded:  280 Time(s)


Windy3.ck
 Description:
ChucK source code for Blown Pipe

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 Filename:  Windy3.ck
 Filesize:  1.8 KB
 Downloaded:  158 Time(s)


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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 5978
Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Mon Mar 22, 2010 10:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

I should also post two of my web references in doing this so you have the whole picture. Here is an excellent web page written for the G2 with algorithms that I am translating into ChucK form:

http://electro-music.com/pm_tutorial/Index.htm

And here is a historical reference point, an article about Ron Berry who has apparently done all of this kind of thing already, just not in custom circuit board form:

http://www.soundonsound.com/sos/1997_articles/jul97/ronberry.html

Enjoy!

Les

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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 5978
Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Tue Mar 23, 2010 2:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Here is the result of this morning's programming, attached below. It is a simple blown pipe model with actual voltage, current, frequency, and delay calculations that describe the electrical signals on the board. Play it as is and you'll hear what sounds a heck of a lot like someone blowing into a pipe. This sounds promising, now to figure out the more complex flute model...

Les


BlownPipe3.ck
 Description:
Blown Pipe model that sounds a lot like a blown pipe.

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 Filename:  BlownPipe3.ck
 Filesize:  2.79 KB
 Downloaded:  147 Time(s)


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Inventor
Stream Operator


Joined: Oct 13, 2007
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Location: San Antonio, Tx, USA
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PostPosted: Tue Mar 23, 2010 10:50 am    Post subject: Reply with quote  Mark this post and the followings unread

I've done some more modeling based on the G2 modeling web page and arrived at a passable flute model in ChucK, posted below. The quality of the sound is very sensitive to the gain values which must be tuned to produce the desired sound. Also if the low pass filter is lowered too much, the thing wails in feedback oscillation, ouch! So there is much to learn before prototyping a circuit.


Flute1.ck
 Description:
The basic flute model in ChucK

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 Filename:  Flute1.ck
 Filesize:  3.03 KB
 Downloaded:  149 Time(s)


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Inventor
Stream Operator


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Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Tue Mar 23, 2010 1:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

I ended up recoding the Jet function X^3-x and suddenly the flute really came to life! I must have had an error in the model. Attached is the latest flute ChucK file and an audio sample.

Les


Flute2 Demo 20100323 1623.mp3
 Description:
Flute2.ck demo

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 Filename:  Flute2 Demo 20100323 1623.mp3
 Filesize:  1018.37 KB
 Downloaded:  290 Time(s)


Flute2.ck
 Description:
Flute2.ck

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 Filename:  Flute2.ck
 Filesize:  3.11 KB
 Downloaded:  145 Time(s)


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Dan Lavin



Joined: Nov 09, 2006
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Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Tue Mar 23, 2010 2:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, the higher notes sound especially flute-like
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Inventor
Stream Operator


Joined: Oct 13, 2007
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Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Tue Mar 23, 2010 6:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Dan, and a huge thanks to all those who contributed to this body of knowledge. All I'm doing here is implementing their designs in analog circuit board form.

I added vibrato which was easy, and I've created a block diagram of the Flute modular synthesizer circuit board. It corresponds closely to the software so hopefully it will work properly.

Les


FluteBD.pdf
 Description:
Flute circuit board block diagram

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 Filename:  FluteBD.pdf
 Filesize:  11.86 KB
 Downloaded:  175 Time(s)


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Stream Operator


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PostPosted: Tue Mar 23, 2010 7:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh, and I must thank Chet Singer for the web page and G2 model describing the algorithm, of course.

Les

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electri-fire



Joined: Jul 26, 2006
Posts: 535
Location: breda nl
Audio files: 4
G2 patch files: 4

PostPosted: Thu Mar 25, 2010 12:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
I ended up recoding the Jet function X^3-x and suddenly the flute really came to life!


Yes, the Flute2 Demo 20100323 1623.mp3 is way better than your first mp3.

Your block diagram is rather more complicated than I expected. Me and my friend Rix made a very nice flute patch on his clavia G2, the main feature being noise as the sound source, and a key tracking resonant filter. Velocity was patched to resonance. With low velocity we got a lot of blow noise, as we "blew" louder the self oscillation of the filter increased the pitch component of the sound.
Well, it's been as while ago, but I think we also had a velocity to Envelope depth to resonance, but it was a fairly simple concept really, not a VCO in sight, and it turned out very expressive and natural sounding.
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frijitz



Joined: May 04, 2007
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PostPosted: Fri Oct 01, 2010 1:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
I should also post two of my web references in doing this so you have the whole picture. Here is an excellent web page written for the G2 with algorithms that I am translating into ChucK form:

http://electro-music.com/pm_tutorial/Index.htm

And here is a historical reference point, an article about Ron Berry who has apparently done all of this kind of thing already, just not in custom circuit board form:

http://www.soundonsound.com/sos/1997_articles/jul97/ronberry.html

Enjoy!

Les

I worked on analog PM a bit also. Look Ma, no BBD!
http://home.comcast.net/~ijfritz/pm_over.htm

Very Happy

Ian
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Inventor
Stream Operator


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PostPosted: Sat Oct 02, 2010 2:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Neato Ian! Thanks for sharing!

Les

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jeff-o



Joined: Jul 19, 2009
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Location: Ontario, Canada

PostPosted: Mon Oct 04, 2010 11:49 am    Post subject: Reply with quote  Mark this post and the followings unread

Very cool. Maybe once I'm finished with my laser guitar, I'll have to build a laser flute! Wink
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Dan Lavin



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PostPosted: Tue Oct 05, 2010 1:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ian Quoted:
Quote:
I worked on analog PM a bit also. Look Ma, no BBD!

Shocked
Ian, you obviously have way more patience than me! That's awesome!

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