This week I attended Music Hack Day at the Drexel Excite Center.  There were many incredible projects there to investigate, as well as some seriously funky live music and some cool folks, all coming together for a 24-hour musical hackathon. The creative atmosphere was pretty inspiring, and out of this was born a weird new hybrid musical instrument -- the Electric Wurlitzharmonica, or the Wur-monica, for short.

With the Wur-monica, I have found a novel way to amplify a harmonica.  The Wur-monica does not have a microphone or pickup of any kind inside. Instead, the Wur-monica relies on the electro-acoustic properties of the instrument itself as a signal source. In fact, the Wur-monica is based on the same elegant principle as my beloved Wurlitzer 200A electric piano (hence the name). 

How it works:
The original Wurlitzer Electric Pianos of the 1960s were gorgeous machines with a really interesting way of generating sound: instead of strings, the piano had large reeds struck by hammers (see picture). The reeds produced a signal using an ingenious electrostatic principle: the reeds were charged up to hundreds of volts, so that they formed a capacitor with the adjacent ground plate.  When the reeds vibrated, this capacitance changed, pushing electrons back and forth to magically produce ethereal honks, buzzes, crunches, and chimes. If you think about it, a condenser microphone also works in much the same way (except with parallel plates instead of vibrating reeds).  In a sense, each Wurlitzer piano reed is its own condenser microphone.

The Wur-monica works using the same principle as the Wurlitzer piano. Each brass reed inside the Wur-monica is mounted on a brass plate, but does not touch it.  This creates a very small capacitance between the reeds and the plate.  When a reed vibrates, this capacitance changes, creating a signal that can be amplified.  Again, no mics, pickups, or piezos are needed -- wires are connected directly to the reeds, so that the reeds themselves produce their own electrical signal.

The main advantage of this technique is that it is immune to feedback from the speakers, because the device does not pick up airborn sound, but rather the raw vibrations of the metal parts. Of course, I'm also hoping to maybe capture a little of that crunchy, magical, soulful Wurlitzer sound in a pocket-sized instrument.

This project is only a proof of concept, so I didn't spend much time refining the circuitry, the method for mounting the reeds, or the intonation, for that matter. In fact, I only bothered to mount seven of the reeds, and one of them is still kind of wonky and shorts out the circuit if I blow too hard (you can hear it shorting in the video). Still, after only a few hours of hacking, I was pretty pleased with how the prototype looks and sounds. 

Please check it out and leave me some feedback!  And if you like classic devices updated with new electronics, check out my USB Typewriter instructable, too. And please vote for this project in the Pocket Sized Contest!  Thanks!

First Test:

Final Test (just before getting dizzy and passing out):

Step 1: Parts Needed

You will need:

Perf board
Insulated wire
Magnet wire
LM358 op-amp
Resistors (1MΩ, 2MΩ, 22kΩ, 10kΩ, and 4.7kΩ)
Potentiometer (100kΩ)
Capacitors (22nF and 1uF)
1/8 inch instrument jack
Power supply that produces both +48V and +12V (I used a Behringer Phantom Power Supply)
Harmonica (I used a Hohner "Bluesband")
An amp for testing (I used a computer speaker from RadioShack)
Tools and stuff

You will not need any magnets, microphones, piezos, guitar pickups, or anything like that to do this hack! That is what is so cool about this project: the harmonica will become its own microphone!
Hi there again... I was thinking about this some more overnight, and did some reading up on the principle at work here, and on different electrostatic organs. Reading about the Hohner Pianet (https://en.wikipedia.org/wiki/Pianet) and taking off from the comment made by rimar2000, below, I suggest that a cool thing to try out would be to mount a strip of copper to the inside of the coverplate, above the reeds crossing them all perpendicularly at their tips, and use that as the charged capacitor. You could use the superglue trick to isolate it from the metal of the coverplate (or actually you could use a cheap Piedmont Blues harp, which has plastic covers). This seems to be how they do it in the Pianet's from the 60's that apparently had a great tone... <br> I may give this a try when I have some free time next week, as I actually have a small powered preamp I use for a Sony electret condenser mic, which may work for this. Those type of mics uses the same capacitance principle as this pickup, but I'm not sure if there's enough voltage in my power supply (it uses a 9volt battery) to power this sufficiently... I also have several &quot;junk&quot; harps laying about, and some extra copper reed-plate material that I could use for the charged plate... I'll let you know what I come up with!
<p>Hey there did you ever try this out?</p><p>I am pretty interested in aplying this to my melodica.</p><p>Cheers from Germany</p>
<p>This is really great! I think using this technique to amplify melodicas or akkordeons might work even beter, since you could mount all the electronics into the instrument housing. </p><p>I really want to try this out on my melodica when I have the time for it. It would be so sweet to run it through a bunch of funky guitar pedals without feedback issues or whatsover! </p>
<p>Is your 1uf cap polarized ?</p><p>What wattage or you using for the resistors ?</p>
<p>this is awesome but you cant really hold it right with all the stuff on the top. I play the harmonica and this would be cool to have :)</p>
<p>wow, this is the most beautiful thing.<br><br>Thankyou so much</p>
Cool, also I couldn't even pronounce the name it.
This is really really really really really awesome. I am a harmonica player and an electronics tinkerer, and I would love to beta test this for you. I can think of two suggestions right now: 1) you'll get better results using a better quality harmonica. The reeds are better (stiffer) and you won't need to reshape them to keep them in their slot. I'd recommend a Hohner Special 20 harmonica. 2) There is an easier, less damaging way to remove the reeds: file down the nub of a set of grometing pliers until it's the same diameter as the rivets holding the reeds on. Then, you can just pop the rivets out. I do this all the time, as the reeds on harmonicas eventually fail due to stress fracturing, and need to be replaced. I can show you a picture of the tool I use (made from a cheap set of grometing pliers from harbor frieght). <br> <br>I have a question, though: is the amplified note the same as the one the reed is playing? i.e., does the capacitance change of the vibrating reed have any relationship to it's vibration frequency? <br> <br>Seriously, I want to beta test this for you. Check my page for my instructables relating to harmonica, and links to my youtube so you can hear my amped harmonica playing. I think this has the possibility of revolutionizing the harmonica world. To my knowledge, there are only three other attempts at doing something like this: one using small piezo pick ups, one using laser pickups, and one using magnetic pickups. All of them are bulky and expensive, and your solution here looks to be simple, cheap, and effective. I'm down to help, so let me know!
Thanks -- I did think about the plastic screws and spacers, but I didn't see an easy way to remove the pins -- thanks for the suggestions! However the real drawback of this design is that condensation forms on the reed plate and shorts out the voltages. This only occurs when you blow. I believe heating the plates to above body temperature may solve this problem -- but may cause others.
Also, instead of superglue, it's probably better to drill the holes out, tap for 0-80 screws, and attach them using plastic screws. Put some sort of insulating material under the reeds where they attach to the comb (probably nail polish or dried superglue would work). Then you, won't have the issue of the reed not lining up once the glue has dried.
Genius! We will have to invent a new genere of music for this!
Great idea! <br> <br>But I think you don't need to disassemble each reed. You could have all them as ground, and a common bus, isolated from the plate, as captor.
That may well be true. It would increase the capacitive load on the reeds, but probably not enough to weaken the signal. Great idea-- let me try that next!
It may also be that the plate might &quot;shield&quot; the reeds from influencing the captor, since in general the plate will be much closer to the captor than the vibrating reeds. I wonder what the waveform would be if there were such a captor on both sides of the plate.
really interesting invention man! congratulations!
Is there any shock potential here? Kissing a mike and getting jolted is no fun.
The 2Mohm resistor should prevent a painful shock from the power supply. And the capacitance of the reed bar is probably in the picofarads, so it will not shock you.

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