Round Slide Harp | Adrian Freed

Series: alt.ctrl activities; builds on Gametrak and Harp; Spatial arrangement

A harp large enough for groups: its strings are Gametrak tethers, bound together by a movable ring. Its upright, round form lets walk-up groups play together, seeing each other through the strings. The ring is playable too: its vertical, sideways and twisting motion is sensed, and it can help or hinder plucking and pulling particular strings, so players have to listen to each other. A handful of Gametraks connect to Max/MSP through a multiport USB hub.

Visitors of several ages around the Round Slide Harp: red tethers run from Gametraks arranged in a circle on a round base up to a disc at the top of a central pole, with an orange ring part way up binding them together. — The Round Slide Harp at Maker Faire.

Materials

Item	Amazon	eBay
Several Gametrak controllers		search
A multiport USB hub
A ring to bind the strings together
The frame (in the photograph, a round base and a central pole with a disc at its top): to be specified.
A computer with Max/MSP

Tools

Tools not yet listed.

Skills

Skills not yet listed.

Instructions

Instructions not yet written.

Variations

Variations not yet written.

Related resources

Round Slide Harp, the instrument's page, with a video

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 "Round Slide Harp", the activity at https://adrianfreed.com/build-round-slide-harp.html.

Write a Max patch, or a program, for a round harp whose strings are the tethers of several Gametraks, connected to the computer through a multiport USB hub and bound together by a movable ring. The Gametraks are identical devices: let me tell them apart by pulling one tether of each.

Detect plucks and pulls on each string. The ring's vertical, sideways and twisting motion is sensed too: ask me how before writing that part.

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/)

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.