Experimental Luthier Workshop: Hacking Chordophones


Several waves of harmonic oscillations occur when a string vibrates. The space between two oscillations is called a node. As a rule of thumb, there is always one node at the bridge and nut and one in the middle of the string among others in between.

When a string is plucked, you may notice that it moves the most in the middle. That is because the impedance decreases towards the middle increases at its ends. Impedence important to think about when manipulating strings because they behave differently depending on where you actuate them.

The pitch of a string is determined by these variables – length, tension, mass, and weight.

Loose, longer, thicker and/or heavier gauge string = lower the note

Tighter, shorter, thinner, lighter string = higher note

Tuning: The first prepared string instruments could have been returned and detuned instruments. This is mechanically the least challenging. Below are some recipes for tuning your instrument.

  • Tune to a chord
  • Reverse or shuffle the order of strings to inspire a new fingering style (note: the nut may have to be altered to accommodate varying diameter strings)
  • Tune courses of strings in unison or in octaves. Try detuning on of the strings so that it is slightly sharp or flat with the rest of the course to produce a chorusing effect
  • Research other musicians who have experimented with tuning and create your own recipe list of tuning specifically for your instrument

Materials: Strings can be made of any kind of material that is resilient enough to vibrate such as nylon, steel, animal gut, rope, silicone, rubber, and elastic. Here are some recipes to explore substituting different types of string material.

  • Bungee cables and rubber tubing as bass strings
  • Fishing line or weed wacker line replacing nylon strings
  • Long springs from reverb microphone toy used as reverberating drone string: This works well on both acoustic and electric instruments
  • Partially unraveled music wire


Depending on their makeup, strings can be plucked, hammered, bowed, scraped, or magnetically bowed to produce various tones. Here are some recipes to explore your options.

Hammering and Hitting

  • Wooden drumsticks, rubber, felt, and wood mallets, hammered dulcimer mallets: Beat the strings near the bridge for a hammered dulcimer or piano effect
  • Percussion Mallets on hollow bodies: Make drum sounds that either resonate throughout the body of an acoustic guitar or throughout the body/strings/pickups of an electric guitar.
  • Drum Brushes: Create random crackling and scratching noises over a pickup or on a soundboard.
  • The bones of your fingers: Use the boney part of your finger to tap strings near the bridge to produce muted hammering effects.
  • Look around the kitchen for egg beater, wisps, wooden spoons, and forks: All of these are great percussion instruments.


  • Try making your own plectrums out of various types of material such as credit cards, felt, leather, latex, cactus quills, feather quills, and wood. What types of shapes can you come up with? What other ways can you hold the plectrum or attach it to your fingers/hand?
  • A motorized plectrum (The Weed Wacker): Find a DC motor from a personal fan or toy add a tie wrap to the end of its shaft and fix it to your instrument. This will produce a mandolin-like effect.
  • Finger-tips and fingernails: Classical guitar players and folk/blues players often use their fingernails to pluck strings. Try using your fingertips instead. This can produce a mellower tone.

Bowing and Scrapping

  • Corrugated metal and plastic forks make great scrapers. Use them like you would bow a string.
  • Fingernail files or needle files for more scraping sounds.
  • A violin or cello bow on a guitar or banjo.
  • Purchase or make your own E-bow. E-bows use feedback to electromagnetically induce the strings to vibrate. It’s basically a pickup-amp-output-coil circuit like an electric guitar circuit but much much smaller and more controllable.
  • A rotary mechanical bow. Try using a Dremel tool with a felt buffer wheel to bow a string. You may need to add rosin.
  • Bowing with fingers and powdered resin: Covering your hands or gloves in resin, you can pinch strings to resonate them running your finger perpendicular and parallel. This may also give you some extra control to incorporate into your technique

Notes on Actuating Strings

Many prepared guitar/string instrument players have an arsenal of mallets, bows, and scrappers. Get yourself a bag or a box to keep them together so you can bring them to performances and practices. Try combining the use of one tool with another so you can quickly change within a piece that you are playing. I am always looking for my favorite tool for the job each time I write a piece. Don’t be afraid to develop your own either by gluing/binding parts together or designing an actuator to print on a 3d printer or laser cutter. Here are some designs that I made that you are welcome to use…



The bridge transmits the tone of a vibrating string to the body of an instrument. In turn, the instrument’s body resonates back to the string. This is how an acoustic string instrument is amplified. Bridges come in many sizes and shapes and can be designed to produce notes that rattle, sizzle, and/or ring.

Tromba Marina Bridge
Ebow Schematic

Sitar Bridge
Ebow Schematic

Kora Bridge
Ebow Schematic

Koto Movable Bridges
Ebow Schematic


Buzzing and Rattling strings. Adding a buzzing bridge or a rattle to a string can produce a seemingly louder effect to an instrument. Below are just a few recipes…

  • A ballpoint pen spring or thin wire wrapped over a string: Try moving the spring along the nodes of the instrument and notice the varying rattling effects. This is also a nice way to isolate the rattling effect to one string
  • Mini clothespins, hair clips, or alligator clips: This falls somewhere between rattling and actuating as the clothespins or clips produce a hammering/rattling effect on strings below or above as the piece moves with the vibrations of the string.

Making Your Own Bridges

If your instrument has a moveable bridge you can replace it with a bridge of your own design. For example, you could give a violin a tromba marina bridge or guitar a sitar bridge. Here are some designs of bridges that I have put together for you to laser cut or modify for your own purposes.

Tromba Marina Bridge
Kora Guitar Conversion Bridge
Sitar Bridge
Banjo Bridge
Single String Movable Bridge

Bodies and Resonance

Body Types
Hollow Body Acoustic and/or Electric
Semi-Hollow Body
Solid Body

Resonator Guitar

Stroh Viola
Op Amp

Empty Body/Frame: This type of body accommodates the swapping of various resonance chambers IE: Baschete Balloon Guitar
Op Amp





Op Amp

Op Amp

Op Amp

Op Amp


Piezo: Contacts sound transmitted through solid objects.

Volume Control Pot

Magnetic: Receives magnetic fluctuations transmitted through vibrating ferrous metal such as steel strings

Volume Control

Volume Control Wiring

Tone Control (Passive Low pass Filter)

Tone Control Wiring

Pickup Box

Separating outputs or multiple pickups to multiple amps

Tearing or modify the speaker

Further Reading and References

Guitar Setup Guide


Nice Noise: Preparations and Modifications for Guitar by Bart Hopkin and Yuri Landman

The Luthier’s Handbook: A Guide to Building Great Tone in Acoustic Stringed Instruments by Roger H. Siminoff


Bart Hopkin’s Windworld – Bart Hopkin’s has been publishing extremely useful resources for experimental-musical-instrument-makers for over twenty years. For such a modest personality, he is a well of knowledge

Stewart Macdonald – Should be Stewart McDonalds because they are the biggest supplier of reasonably priced Luthier parts. They have great How-To videos as well.

Sound Artists/Musicians who Make Instruments

Pierre Bastien
Baschet Brothers
Luigi Russolo
Bradford Reed
Yuri Landman
Nic Collins
Godfried-Willem Raes
Shawn Decker
Nick Baginski
Harry Partch
Paolo Angeli
Eric Leonardson

More to come…