Picture of The Arduino OctoSynth
What is the OctoSynth you may ask? The octosynth is a polyphonic synthesizer that is able to produce eight Pulse Width Modulated tones that form together a musical scale. In English terms, it is a 8 key electronic organ that can play more than one tone at once but only one scale.

Special thanks to Joe Marshall who wrote the very useful code.

As suggested in the title, it runs on Arduino.

So before we get started, let's see what is sounds like. Shall, we?

And and explanation would be nice.

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Step 1: Parts of The OctoSynth.

Picture of Parts of The OctoSynth.
You will need:
An Arduino
12 Male headers (2 together and another six together. Also, another 4 together(Optional))
8 Unifomly LONG Wires ( By long I don't mean 3 meters but it means a decent 10 inches or maybe, 20 crentimeters.)
A Certain Amount of Copper Tape (Get a roll to be safe)
Enclosure (I used styrofoam as a base but if you want an enclosure, which is totally fine, you can use one. The length will depend on the wideness of you choose.)
Power Jack and Battery

Step 2: Program.

Picture of Program.
Upload the code below to the Arduino.

Open with the viewer of your choice.

Step 3: Build.

Picture of Build.
  1. Measure out how much material you have with the copper tape. Make sure you leave enough enclosure/foam to accommodate for the spaces in between to prevent shorting.
  2. Cut that much tape and maybe a millimeter more.
  3. Divide the tape into eight sections by folding.
  4. Solder ONE wire to each piece of tape.
  5. Solder male headers to the tape. Six pieces to six headers for six in puts and then a pair of two for the other two inputs; Digital 6 and 7.
  6. Order will now begin to matter. The first one (Analog 0) will go on the far left of the enclosure/foam. Analog 5 will go to the input 6 so it is la on the musical scale. 
  7. Digital input 6 is ti and input 7 is high do.

Step 4: Wiring.

Picture of Wiring.
Plug in the wires to the Arduino. Connect the speaker to Digital Output 11. You may need to use headers.
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DimitarD22 days ago

can someone help me?

i'm really bad with programing and i don't know what to do.

Arduino: 1.6.1 (Windows 7), Board: "Arduino Uno"

sketch_mar26c.ino:807:5: error: expected unqualified-id before string constant

Error compiling.

jo_mo3 years ago
Really great work. I made one and it sounds sweet.

would you please assign me the code of the project

blinkyblinky (author)  jo_mo3 years ago
Very good job! Achievement patch coming soon!

sketch_mar25a.ino:781:5: error: expected unqualified-id before string constant

Why am I getting the error caused

Ploopy made it!1 month ago


Here's my messy version of it. I added volume control.

Nice code :)

Photo on 2-16-15 at 6.19 PM.jpg
amaria91 month ago

can the same code be used for lilypad?

saymowan6 months ago

Nice project, simples and amazing! :-))

orangeisnon9 months ago

First off, great project. I haven't read through all of it, but I get the idea.

Now, how feasible would it be to get this running using something besides the copper tape? Say, mmm, bananas?

Basically, could one use the same wiring and code from this and use bananas (like this: People know me as the banana guy, and I think it would be fun to make a video of me playing a banana synth. I've got all the parts (and the nanners) but the linked 'able doesn't use Arduino.

rogeliotorlao10 months ago

can you add more effects to choose from? and add more keys .. lt is a brilliant project

What's the point of havin the headers couldn't u just plug the wires straight in the arduino
The headers are thicker than the wire and are more likely to stay in the Arduino headers; they make the project more stable; also, it means you wont have to dig through to figure out which wire is which when you leave the project on hold and then suddenly pick it up again.
What gauge wire
What do you mean?
i´m trying to make some like this but to use with Fl studio but i can´t figure how to change the code, any clue? (sorry my bad english)
blinkyblinky (author)  igneonumous1 year ago
I am not as advanced as FL Studio so I can't really help you there. Sorry.
agomes61 year ago
thanks for the instructable!

i am running into a problem though...i built mine and it only plays the first 3 keys, the remaining keys will play just fine if i touch the 9v battery...any thoughts?
blinkyblinky (author)  agomes61 year ago
What do you mean "touch" the 9 volt battery?
if i am in contact with the batteryor the arduino itself it plays, otherwise it will just plays the first 3 keys odly enough
blinkyblinky (author)  agomes61 year ago
Check the amount of power from the 9 volt using a multimeter.

If that checks out, look and see if you have proper connections.
battery was at 8.xx V capacity, the connections must be good, otherwise it wouldn't play properly attached to a usb port (does this make sense?)

I am using 1.2cm copper tape and they are 1cm apart from each other, I wonder if i am having some sort of capacitance issues. I will record a quick video and post it tomorrow morning
blinkyblinky (author)  agomes61 year ago
Sorry for the late reply but are you still having problems?
What kind of power source did you use? You mention a battery, but what kind?
blinkyblinky (author)  MaxTheFilmDude1 year ago
9 volt.
blinkyblinky (author)  blinkyblinky1 year ago
9 volt battery
mabostudio2 years ago
very cool gizmo! we did this for burning man and people were awed!
thanks for the instructable.
I do have one question. Is it possible to wire this to a shiftbrite LED and have it play both colors and sound? I looked at the code but my novice level is a major handicap. how do you suggest this can be implemented?
Freaky2712 years ago
to what pin I connect the speakers?
blinkyblinky (author)  Freaky2712 years ago
Pin 11
umfan1102 years ago
could you add a pot to change the frequency of the synth
Emanuelgeo2 years ago
How did you connect the speaker up to the arduino board?
mocm3 years ago
any chance of midi out?
blinkyblinky (author)  mocm3 years ago
I am assuming you posted three of the same comments and then deleted two or Instructables just spazzed.

Not really. I have wanted to learn how MIDI works for a long time and what the uses could be...

If someone could write a good article (simpler than Wikipedia and other websites) I would probable try and add MIDI. I still have no idea about its application.
Hi, thanks for the replay...
i just sing up on the Instructables site and i mess with the comments ☺
blinkyblinky (author)  mocm3 years ago
Its okay. Sorry for no MIDI yet.
if you have sum time check my funny sound modules...
blinkyblinky (author)  mocm3 years ago

Now you just need How-Tos.

(I really like the FA one but I only examined a few. Any suggestions on which ones I should watch?)
LucDaRocka13 years ago
why eight? because u wanted an octave?
blinkyblinky (author)  LucDaRocka13 years ago
Of course! Many (simple) songs can be accomplished with an octave. But, I didn't design the code.
AndyGadget3 years ago
Just a technical point :- You're not actually using that as a capacitive sensor, which is a non-contact form of sensing.  You are affecting the arduino input by a combination of changed resistance and hum pickup.
To convert it to proper capacitive sensing, put a thin sheet of non-conductive film over the row of keys.  You may need to enter a calibration value into the code to set the switching threshold.
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