Hyperacoustic instruments: Computer-controlled instruments that are not electrophones

This paper describes a musical instrument consisting of a physical process that acoustically generates sound from the material world (i.e. sound derived from matter such as solid, liquid, gas, or plasma) which is modified by a secondary input from the informatic world. This informatic input selects attributes such as the frequency range of the musical note being sounded, while the acoustic process is kept in close contact with the user, to ensure a high degree of expressivity. In one example, ice skates with acoustic pickups are used to play music while the skater simultaneously controls a bandpass filter with a hand-held keyer and wearable computer. Each skate works much like the bow on a violin, allowing the player to hit, scrape, rub, or "bow", the ice in various ways to create a wide variety of musical textures. Additionally the player can select sound samples on a per-note basis and then "scratch" out a melody or harmony (playing multiple samples at once) on the ice on the rink like a team of disk jockeys (DJs) working together to "scratch" an array of vinyl records. Because the grooves on an ice rink are made by the player in a freeform fashion, there is much more room for variations in musical timbres and textures than with the fixed grooves of a record. Rather than merely using the keyer to trigger musical notes through MIDI note on/note off commands, we create acoustic sound through a physical process such as skating, and then turn those physical sounds into musical notes with the handheld keyer that functions as a modifier input. This combination combines the expressivity of non-electrophonic musical instruments like the violin with the flexibility of electrophones like the sound synthesizer. As a further contribution of the paper, a general taxonomy of acoustic transducers and a link to physical organology is provided, in which the top-level of the taxonomy is the state-of-matter in which the transducer operates.