Tethertonium
Series: alt.ctrl activities; builds on Gametrak and Trautonium; Spatial arrangement
With a conductive fingerboard, and conductive thread attached to a tether, the Gametrak's footswitch input can time touches accurately. Together they simulate a trautonium.
Materials
| Item | Amazon | eBay |
|---|---|---|
| A Gametrak controller, with its footswitch input | search | |
| Conductive thread | ||
| A conductive fingerboard (in the paper's photograph, copper-coloured strips) | ||
| A computer with Max/MSP or Pd |
Tools
- Screwdriver
- Soldering iron, to set the Gametrak up for a computer (see Set Up a Gametrak for Music) and to wire the footswitch input
- A multimeter with a continuity test, to find the footswitch input's contacts
Skills
- Working with conductive thread
- Soldering
- Mapping controller data to sound in Max/MSP or Pd
Instructions
- Set the Gametrak up as in Set Up a Gametrak for Music.
- Lay the conductive fingerboard under the tether's path.
- Attach conductive thread to the tether where it crosses the fingerboard.
- Find the footswitch input's two contacts: unplug the footswitch, set a multimeter to continuity, and test the contacts of its plug in pairs while pressing and releasing the pedal. The pair whose continuity changes with the pedal is the one to use.
- Wire the thread and the fingerboard to those two contacts, through a plug that fits the Gametrak's footswitch socket, so that pressing the thread onto the fingerboard closes the input, as the footswitch would. Leave the footswitch itself whole.
- Check it: touching the thread to the fingerboard changes the footswitch reading (see the identify step of Set Up a Gametrak for Music). If it reads the wrong way round, because the pedal opens its contacts rather than closing them, invert it in the software.
- Map the readings to sound: for example, the tether's extension to pitch, with touches starting and stopping notes in time.
Variations
- Use both tethers, each over its own fingerboard strip, as in the paper's photograph. If both close the one footswitch input, tell the touches apart by which tether moves.
- Sense how hard the thread is pressed, as the trautonium's player set the volume by "the pressure of the finger on the wire and board" (Trautonium, Wikipedia): put piezoresistive fabric under the thread and read it on an analog input with a pull-up resistor, for example with your own microcontroller as in Replace the Gametrak's Electronics.
- The Ondestrak takes the same idea toward the Ondes Martenot.
Related resources
- Musical Applications and Design Techniques for the Gametrak Tethered Spatial Position Controller, Freed and others, SMC 2009, section 4.7
- Trautonium (Wikipedia)
- Favorite eTextile Materials, for conductive thread
Coding Prompt Build Block
A prompt to give a coding assistant, to start the code for this activity. Copy the box, answer its questions about your board and pins, and test what comes back on the bench before you rely on it.
I am building "Tethertonium", the activity at https://adrianfreed.com/tethertonium.html.
Write a Max or Pd patch, or a program, for a Gametrak whose tether carries conductive thread that closes the footswitch input when it is pressed onto a conductive fingerboard.
Map the tether's extension to pitch, and start and stop notes with the footswitch input, in time with the touches. Let me invert the footswitch reading, in case a touch reads as a release.
Libraries to explore:
- o.io.gametrak (CNMAT MMJ Depot): CNMAT's Max patch for the Gametrak: it opens the device and outputs /left/x, /left/y, /left/z, /right/x, /right/y, /right/z and /footswitch, the angles scaled from -1 to 1 and the extensions from 0 to 1 (https://github.com/CNMAT/CNMAT-MMJ-Depot/tree/master/patchers/io/gametrak)
- odot (CNMAT): the o. objects for Max and Pd that o.io.gametrak is built from, with OSC bundles as their data type (https://github.com/CNMAT/CNMAT-odot)
- Max hi object: reads human interface devices, such as game controllers, in Max (https://docs.cycling74.com/reference/hi/)
- Pd hid external: reads USB HID devices, such as joysticks and gamepads, in Pd, on GNU/Linux and macOS (https://github.com/pd-externals/hid)
Before writing anything, ask me what I am using: the board and its pins, or the software (such as Max, Pd or Python), and check its documentation for what this needs. Put the pin numbers, ranges and other settings in one block at the top, each with a comment. Say which of the libraries above you use, and why. Start with a test that shows the raw readings, so that I can check the wiring and the ranges before the rest.
This activity by Adrian Freed is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0): you may share and adapt it with attribution, for non-commercial purposes such as personal projects and teaching, and you must share adaptations under the same licence. Product names and links belong to their suppliers.