There are 2 different sizes of archs, small and big. They mix together presumably according to the pictures in the document on the freedom park proposal. For both sizes, it is possible to make them digitally interactable the same way and let their physical shapes change the type of interaction (sitting as opposed to climbing, etc). We can place an IR rangefinder inside the arch, as well as the laser trip wire right next to it. When the laser is tripped, the input from the rangefinder will be read and a note will be played – maybe a piano note. The notes will always be in-tune as opposed to “slide-able” with the tone, since the rangefinder was fidgety when we tested it, but accurate to a certain degree (always in ranges but not specific values, we’ll post on this information soon).
With one of these setups per arch, we use all our sensors. We can also put 3 photo sensors per arch, and covering a photo sensor causes the sound to drop an octave, allowing for different types of interactions as more people come along and cover the sensors and allow the sound produced to change. Perhaps one should not be interactable if it is used to sense sunlight for power purposes.
As for using multiple IR emitter/detector pairs: Music theory is (at least according to Bach’s way of writing it) strongly based off the triplet chord, where there’s the base note, and then you play the note a 3rd above it, and then the note a 3rd above that one (usually in a major scale, for example C E and G). The bottom one could trigger the bottom of the chord, middle triggers the middle, top triggers the top of the chord. The bottom note would be varied based on the IR rangefinder.