Updated Apr 27, 2009 by cathedrow
Labels:	auduino, arduino, Featured

Auduino

Details of the Auduino synthesiser

Introduction

The Auduino is a sound synthesiser based on the Arduino platform. It works on all Arduinos running at 16MHz - everything from the original Arduino serial to the Arduino Mega. It uses granular synthesis techniques to generate a distinctive filter-sweep sound that had much more character than boring square waves.

Have a look and a listen

Synthesis model

Sound is generated by playing the same noise ('grain') repeatedly at very high speed. This merges into a tone that is an audible hybrid of the repetition rate and the original grain. It sounds quite similar to an oscillator with two resonating bandpass filters, although the different architecture means there are lots of additional interesting noises at parameter extremes.

The grain consists of two triangular waves of adjustable frequency, and adjustable decay rate. This is based on FOF synthesis model, but using triangle waves instead of sine and using a rectangular window.

The repetition rate is set by another control.

Programming the Arduino

Download the source code from the the Tinker.it Google Code site. Load it into the Arduino environment, set up your board type and serial port, then hit the Upload button. Done. If you've never used Arduino before, you'll need to download the development software from the Arduino site.

Construction

Auduino uses 5 controls. You can use anything that generates a 0-5V analogue signal, but the prototype uses five 4.7Kohm linear potentiometers. Connect one side of each potentiometer to GND. Connect the other side to the 5V pin on Arduino. Connect the middle (wiper) pins to Analog inputs 0 to 4 on the Arduino.

The audio comes out of Digital pin 3 (or pin 11 on ATmega8 Arduinos). The prototype uses a 1/4" jack socket, with the tip connected to pin 3 (or 11 on ATmega8's) and the shield connected to GND. Plug the other end into an audio amplifier, and you're good to go.

The Arduino can drive a small piezo, speaker or headphones directly. Strictly speaking it outputs at 5V rather than the 1V line level, but most amplifiers don't seem to mind.

Auduino community

We now have a group on Google Groups. Show off your hacks, or get help with your Auduino projects.

Auduino controller hacks

The Auduino can take any analogue signal and make it audible. Add a Light Dependent Resistor, you have an instant theremin. Add a linear softpot, instant keyboard or ribbon controller. The Arduino Playground is a great place to get new ideas.

Auduino software hacks

Have a look at the loop() function. The controllers are mapped to the synthesiser parameters there. You can really customise the controllers there - adding different musical scales, vibrato, envelopes - whatever takes your fancy.

Start by playing with the pitch mapping. Three mappings are available to start with. Uncomment the one you prefer:

// Smooth frequency mapping
//syncPhaseInc = mapPhaseInc(analogRead(SYNC_CONTROL)) / 4;

// Stepped mapping to MIDI notes: C, Db, D, Eb, E, F...
//syncPhaseInc = mapMidi(analogRead(SYNC_CONTROL));

// Stepped pentatonic mapping: D, E, G, A, B
syncPhaseInc = mapPentatonic(analogRead(SYNC_CONTROL));

syncPhaseInc is proportional to frequency, so the /4 above drops the pitch to a quarter, or two octaves.

Auduino hardcore hacking

If you're really into algorithmic synthesis, have a poke around in the interrupt routine at the bottom of the source code. You'll have to be careful to keep the routine fast, but there is plenty of spare CPU to implement other synthesis techniques.

Comment by brian.degger, Nov 18, 2008

Just making sure, are the Pots Linear? Cheers Brian Degger

Comment by cathedrow, Nov 18, 2008

Very good question. Yes they are - and I've updated the text. Thanks Brian!

Comment by 3vil.0verlord, Nov 18, 2008

Just attach a few buttons over some resistors instead of the pot that controls the freq and you got a keyboard ;-)

Comment by casainho, Nov 18, 2008

Congratulations for this project!! Looks very good :-)

Comment by jesse.freedom, Nov 22, 2008

Just breadboarded this and am playing around with it. With a little experimentation on the controls, it sounds awesome! Can't wait for my softpot to arrive and then I can get some keyboard action going...thanks for sharing this project!

Jesse

Comment by xndr77, Dec 07, 2008

Very nice project! I built one myself to demonstrate the protomodule / arduino enclosure project I've been working on: http://www.flickr.com/photos/machinecollective/sets/72157610797368431/

I think I spent almost 2 hours playing with this baby.. It's amazing! Thanks and keep up the good work!

Comment by cathedrow, Dec 08, 2008

Love it xndr77! Great video, and love the enclosure. Linked up the video for all to see.

Comment by bas682009, Dec 09, 2008

i love the sounds that come out of this, and would like to explore the use of this as a keyboard driven synth. i noticed that one person talked about buttons over resistors to make it a keyboard...

i have seen another arduino keyboard before, but, the sounds that come out of the auduino are much more pleasing to my ear... i also thought about the use of a softpot... are you able to set the pitches to a range of resistances in the software? thanks!

Comment by cathedrow, Dec 11, 2008

@bas682009: One thing to watch with a keyboard - it controls two things - the pitch of the note, and also if a note is playing. Auduino right now allows pitch control, but not note gating. Of course, you've got the complete source code so there's nothing stopping you implementing that. You might want to consider ADSR. As for mapping pitches to resistance: you need to map the keyboard to voltage. I'd look at using a potential divider for that, as a chain of same value resistors. Depending on how you organise the chain, you may need to modify the ADC reading to pitch mapping in the loop() routine. Have a look at the source code.

Comment by p00b0x, Dec 12, 2008

Awesome project! I have been playing with this code and hooked it up so it is controlled from windows through serial rather than the pots. Not as usable as physical pots but it was just something to play with.

once again, great work!

@bas682009: I have changed it so that the values that are used to generate the sound are stored in variables and those variable are updated via software through serial, so yea it can handle the storing the values. I dont even notice any delay when it plays back even though it is monitoring the serial and doing some basic logic from it.

Comment by cathedrow, Dec 13, 2008

@p00b0x: Glad you're having fun.

This comments section is getting a bit long, so I've created a Google Group

That should make things easier when sharing source code, diagrams and such.

Comment by lifeisnoise, Feb 07, 2009

Very cool project, I just got mine working. My kid loves it too. http://noiseislife.tumblr.com/

Comment by goatboyrobbie, Mar 14, 2009

"although any Arduino running at 16MHz will work fine" Does this mean that you can't operate Auduino if your using an Arduino mini pro that operates at 3.3v/8MHz? A newby getting to grips with the Arduino Universe!!! Brilliant project by the way!!, Robbie

Comment by cathedrow, Mar 14, 2009

@goatboyrobbie: It could work with 8MHz devices, but... It would run an octave lower. Also, the PWM would run at half the rate, so the 'whistle' of PWM would be much more obvious. Try it - it will work as is - but I think you'll prefer running it on a 16MHz device.

Comment by goatboyrobbie, Apr 10, 2009

Thanks Cathedrow! I have a couple of mini pro's running at 5v now so it won't matter but on another issue I can't seem to get any real decent sound out of this Auduino! I've checked the wiring and everything's loaded perfectly but it seems very tricky adjusting the pots to hold on to the melody and certainly can't get anything close to that fantastic video demo!! I just wonder where I'm going wrong? Any body else finding that tricky or is it just me? Appreciate any advice, Goatboy

Comment by goatboyrobbie, Apr 11, 2009

All sorted!! Finally got a grip on this little baby!! Between the pentatonic scales and the filter sweeps it'll put you right up there with the old Mongolian polyphonics!!!

Comment by dsikar, May 11, 2009

Thanks Peter K. for your help at openhacklondon. We rushed managed to assemble your circuit, in the end because it was "passive" we had to add some more resistors but got a working prototype in time. Cheers The pedal steel guitar tone control hackers

Comment by baddspella, Aug 15, 2009

dude where can i find the code for "Synthesis model" i searched the site and nothing :S

some one pease link me ? / email me @ baadspella (@) gmail.com

Comment by jesse.juup, Aug 18, 2009

I made one too!

Here's a video of the build: http://www.youtube.com/watch?v=IwV-SKpQAak

Next step is trying to build and add a ribbon controller.

Comment by marcelijzerman, Aug 24, 2009

Great that you share this, easy to understand. Thanks