HDD Actuated Acoustical Instrument

This is the multichord, a one-string musical instrument built by [Christopher Mitchell]. The string is a 20 pound mono-filament thread stretched between a wooden bridge and the read/write head of a hard drive. The idea is that the vibrations of the string are picked up and amplified acoustically by the sounding box that serves as the body of the instrument. The frequency of vibration (pitch) is changed by adjusting the tension of the string through the application of various voltages to the HDD head. A relief spring has been added to the head to take the resting tension off of it, making it a lot easier to fine-tune the settings for each note. A keyboard made of twelve buttons selects each different pitch as the string is plucked.

[Christopher] is continuing to post great hacks; we’ve seen a glove input and a giant VU meter from him in the past. Take a look at the multichord in action after the break.


[via Hacked Gadgets]

27 thoughts on “HDD Actuated Acoustical Instrument

  1. I am imagining a HD controlled Hurdy-Gurdy. Get one with 12 strings and a rotating Rosined Disc… holy crap.
    Note about this design, I noticed the beefyness of your bridge. if you made the bridge ALOT thinner and out of something lightweight and strong (traditionally maple) you’d get alot more volume.
    Awesome Prototype!
    I love hacked together instruments!

  2. @spork.
    Are you seriously posting using my name?

    While that is a cool concept, I prefer a real guitar. For the major advantage of finger picking, I can hit like 5-6 notes in the time that it takes to hit one on the multichord.

  3. “While that is a cool concept, I prefer a real guitar. For the major advantage of finger picking, I can hit like 5-6 notes in the time that it takes to hit one on the multichord.”

    What, an instrument that’s been around for hundreds of years is more fully developed than one that someone developed recently?

    My main concern is that he seems to have limited musical knowledge… He claims a 12 note scale with ‘no sharps or flats.’ His tonic is ‘c at 220 hz’ His writeup suggests this is misspoken, as his charts have 220hz correctly named as A.

    I’d be much more interested in this project if there was some sort of feedback, as the string will undoubtedly stretch with use and cause his instrument to go flat, as his project depends on applying pre-measured voltage values.

  4. @Spork #2

    While a guitar is a cool concept, I prefer a piano. I can hit like 10 notes in the time that it takes to hit 5-6 on the guitar. :)

    It’s a proof of concept- perhaps in a later design it will produce computer controlled sounds that a guitar can’t. No need to be disparaging.

  5. Hey Hackaday, thanks for picking this up. :) Yup, I originally totally spaced on the note frequencies and the fact that 220, 440, 880 etc are A, not C, must have been half-asleep when I wrote the original description that I read in the video. As you noted, I caught myself and eventually fixed the written description.

    The feedback idea is an excellent one; besides the signal processing aspect, the necessary voltage adjustments might be interesting. A looser string would imply that everything would need to be shifted towards higher positive voltage (negative voltages towards zero, positive voltages away from zero). That would be infeasible with the current fixed resistors; suggestions?

  6. @christopher mitchell

    It’s been a while since i spent a lot of time studying electronics, but what if you explored an approach that didn’t depend on resistance to vary the pull of the coil?

    In a high-level sense, what if you developed a set of data that correlated string pitch with tension (ie, with this much tension the string produces this frequency), incorporated a tension meter into the project, and used, perhaps, PWM to vary the tension on the string?

  7. @Spork
    Not to pick nits, but. . .

    Technically the piano is a stringed or string-type instrument. ;) JK – I know/surmise that you meant portables like ukes, fiddles/violins and guitars.

    Who knows where this project will lead. I figure we, Mr. Mitchell included, are only limited by our imagination, willingness to experiment/learn, pocketbook, and free time.

  8. @Aged Cheddar
    Haha, I figured someone would call me on that. It is actually why I called it a string-type instrument instead of the actual category “stringed”. Can’t very well use finger picking on a piano though, can we?

  9. These all sound like good ideas, I’ll certainly consider a PWM scheme if I decide to expand this project. Offtopic, I noticed that Hackaday forgot another of my projects that they featured under my alias, Kerm Martian, the first iteration of my modded TI-83+.

    @Aged Cheddar: free time is the most restrictive of the elements on your list with money a close second, unfortunately.

  10. make it pluck itself when you press a key, add some pickups from an electric guitar. buy a midi keyboard and wire it to a hard-drive speaker. start a band where the audience has to be really, really quiet. and throw in one of those electric-arc speakers because those are the shit

  11. I was getting into it during the intro and then he played the thing. How utterly boring. It’s quiet, it can’t tune many notes because of the tension required and the relative weak strength of a RW head. Just not really the best application for this.

  12. “Technically the piano is a stringed or string-type instrument. ;) JK – I know/surmise that you meant portables like ukes, fiddles/violins and guitars.”

    @Aged Cheddar – if you’re going to nit pick, the Piano is classified as a percussion instrument since it has hammers hitting the strings to create the sound (i.e percussive).

    “take off the lid, and set it on its side, pick away”

    @osgeld – try picking the bottom C on a piano a couple of hundred times. Better still, try it with top C and really give it some wellie, like you’re playing guitar – oh and keep a bowl of ice under the piano to catch your fingers as they slice off.

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