“Greg’s Harp is a new string robot I made for my friend Gregor. After the Pythagotron which is a single stringed bass roboter, this is my first attempt to combine three string units to make a polyphonic instrument.
Pitch actuators
While the Pythagotron features a motor driven carriage which shortens the string to the desired pitch by sliding up and down, for Greg’s Harp I came up with the concept of motorized frets. They make quick changes between chords possible.
Since every moFret needs a dedicated servo and driver, we tried to keep the number of needed moFrets low but still enough to allow for playing every possible triad (e.g. c-minor in at least one inversion). We came up with four moFrets (equals five semitones) per string. The strings are tuned in major thirds, making them overlap one tone (so that string 1&2 and string 2&3 have one tone in common). A software algorithm takes incoming notes, analyses them and sends a playable inversion to the moFret controller.”