This unusual instrument took two months to build and has 49 stepper motors, one for each note, each motor floats above one of 49 disks, which increase in size exponentially as the notes ascend in pitch.
The disks spin together, driven by a single speed-controlled DC motor. When a key is pressed, the corresponding stepper motor is engaged with the corresponding disk in the disk stack, and the disk back-drives the stepper motor. The larger disks are moving faster on their outside edge than the smaller disks, so the stepper motors are driven faster by the larger disks than the smaller disks.
The disks are sized such that all the notes will be in tune relative to each other. The key that the instrument plays in is determined by how fast the disk stack is spinning. A faster disk stack will play a higher key, a slower disk stack will play a lower key.
The speed of the disk stack is a global pitch shift.