Invent a Musical Instrument

 

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We made musical instruments during Riverdale’s Middle School Project Week, wherein students have the better part of four days to dig deep into a project. We talked about and demonstrated instruments from the four known categories (percussion, woodwinds, brass, strings) and discussed how they work and how we could construct instruments that functioned similarly.

We had a number of useful materials on hand:

Thin steel wire (for strings) and small turnbuckles (for tuning)
Small rare earth magnets
A bunch of old power bricks (aka wall warts, aka transformers)
Soldering gear, wire, and female 1/4″ jacks
Guitar cords (male to male 1/4″)
Buckets, vinyl, and grommets (for drums)
Wood, steel, paint for decorating
Guitar amplifier(s)

Most of the students making stringed instruments were intrigued by the idea of making their own electromagnetic pickup so as to be able to connect their instrument to an amplifier. Here’s how to do so on the cheap. This is a great opportunity to talk about electromagnetism and how sound, microphones, phones, etc work.

  1. Using a vise, hammer, or screwdriver, crack open an old power brick. Inside you should find a transformer (coils of thin wire wrapped around stacks of steel plates)guitar_pickup
  2. Remove the transformer and solder the two wires coming from one of the coils to the two terminals of a 1/4″ female guitar jack (the wires may not be long enough, you may need to add wire to do this)
  3. Mount the transformer and the jack under the strings of the instrument
  4. Place a small rare earth magnet (or two) on the transformer just underneath the strings

When plugged into a guitar amp, the vibration of the string disturbs the magnetic field surrounding the magnet. This disturbance induces a current in the coil, which is transmitted to the amp via the jack and the guitar cord. Instant humbucker pickup! A neat trick to show students is to place a phone that’s playing music next to the pickup – the music will come out of the amp too. This is because the fluctuating magnetic field of the phone’s speaker induces a current in the coil just like the string.

Our final jam session didn’t win any awards, but we had fun.

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