Step 1: Part and tools
power source(I used a 9v with an adapter)
4- 5k linear potentiometers
200mm linear SoftPot(you can go smaller than this I just used this length because its what I had)
optional: Arduino holster(I had this made using a MakerBot) for easily removing the Arduino if you want to use it for something else.
all of this I was able to get off jameco.com except the SoftPot which i found at trossenrobotics.com
For the box:
Acrylic pane(found mine at Lowe's)
Weld-On 4(found on Amazon)
Weld-on applicator bottle
Step 2: Wire It Up
First just line up the five pots with the SoftPot. Then wire the first pole of each post together and solder it. The do the same with third pole. Then solder a wire to each of the center poles. The SoftPot center pole needs to connect to the A4 pin, the second pot's center goes to A3, the third pot's center goes to A2, the fourth pot's center goes to A1, and the final pot's center goes to A0. Then on the fifth pot solder another wire to the left and right poles, with the left pole connecting to the 5v pin and the right pole connecting to the GND right next to it. The only thing left is to connect an audio output jack with the hot going to ~3 and ground to GND.
Step 3: Code
I got the code from here: http://code.google.com/p/tinkerit/downloads/detail?name=auduino_v5.pde&can=2&q=
Now load the code onto the Arduino, hook it up to a speaker and check that it works. If not then just go back and check the diagram I made and make sure that you got all of the pots wired correctly and that you got the wires in the right pins.
Now I know nothing about coding but after looking at the sketch for a while I was able to sort of see how it worked. I was able to make some changes to the decays and the second pitch to get the sounds I was wanting, so I would say go ahead and mess around with it until you get the sounds you like even if you are like me and know nothing about coding. Just make small changes at a time and then test it, if you do mess it up too much then you can always just reload the original sketch and start again.
Step 4: Make the Box
Next make a rough cut using a table saw, give yourself some room to work with because you will want to clean the edges up on the router table. With the router you want to make sure the bit is just barely past the guard so that you are only take a small amount off of the edges at a time. Just do this until you reach the the right dimensions. To get the clear edges on your acrylic you will then want to take a torch and run it along the edges, keep it moving or you will burn it which will result in bubbling. This will melt it just enough so that you are left with wonderful smooth and clear edges.
Now its time to fill your applicator bottle with the Weld-On 4. Then one side at a time, press the edges together and place the needle of the applicator in the corner and gently squeeze it as you slowly slide it down the seem. You should be able to see the liquid run through the seem, you will then need to apply pressure to it for a few minutes until the bond has set. Continue this process on each side.
Now its time to figure out where you want the knobs and audio out to go and drill the holes. Acrylic will grip, a lot, so you have to drill very slowly or chunks might go missing, or worse, you end up with a big cracked mess. and you get to start again. Once I drilled the holes I cleaned the edges up with my knife to get the melted bits of and the torch them to gloss them up.
Step 5: Assemble then Play
Now plug in the power and hook it up to a speaker and have some fun. I have ran this through a delay and chorus pedal and you can really get some fun sounds out of it.