INVENTING NEW INSTRUMENTS BASED ON A COMPUTATIONAL 'HACK' TO MAKE AN OUT-OF-TUNE OR UNPITCHED INSTRUMENT PLAY IN PERFECT HARMONY
Steve Mann, Ryan E. Janzen, Raymond Lo, Chris Aimone · University of Michigan Library Repository · 2007
We begin with a case-study of one of our public art installations, a large waterflute, which is a member of a class of water-based instruments that we call "hydraulophones".Hydraulophones are like wind instruments but they use matter in its liquid state (water) in place of matter in the gaseous state (wind).The particular waterflute in question has the unique property that it has never been tuned, and, additionally, due to what would appear to be a theft from an underground vault just before the main public opening, a number of important parts went missing.Additionally, due to some errors in the installation, we had to use some creative and improvisational computation in order to make the instrument "sing" in perfect harmony.What we learned from this case-study, was a specific technique that allows computation to be used to make almost any out-of-tune, broken, or quickly built/improvised instrument play in perfect harmony, as long as a separate acoustic pickup can be used for each note.Our method uses a filterbank in which sound from each pickup is processed with a filter having a transfer function that maps the out-of-tune or otherwise "broken" sound to the desired sound at the desired pitch (optionally with acoustic feedback to excite the original acoustic process toward the proper pitch) without losing too much of the musical expressivity and physicality of the original acoustic instrument.We also propose the use of other techniques such as computer vision to relax the requirement of having separate pickups for each note, while maintaining the physicality of an acoustic instrument.