The Abstract Chord COnstruction and Rendering Device or ACCORD (yeah, yeah, I know) was my class project for MAS960: Principles of Electronic Music Controllers. Basically, it's a MIDI controller/analog synthesizer that provides a means of constructing three or four-voice chordal sequences. Unlike many traditional instruments, control is abstracted such that the user is only able to produce a set of limited, "legal" chords. The interface philosophy also diverges from the traditional approach by providing explicit and separate control over each of the factors that make up a particular chord. These factors are:
Chord type: major, minor, augmented, diminished, and dominant (7th chords only)
Timbre (sine, triangle, or square waveform for the analog synth output)
Triad or 7th chord
These five factors are controlled with separate button banks. There are 16 root buttons (four rows of four), giving about an octave and a half of range. The right hand is responsible for these buttons (see below). Each of the remaining four factors are controlled using a column of buttons positioned under each one of the fingers of the left hand (again see pics below). The index finger selects the chord type, the middle finger the inversion, the ring finger the timbre, and the pinky finger whether the chord is a triad or 7th chord. Each of the control dimensions is non-volatile so that the user does not need to control each factor all of the time.
In addition to the discrete controls listed above, there are two continuous modifiers, volume and arpeggiation. Each of these is controlled using a FSR under a palm pad. Increased pressure under the left palm will increase volume (velocity) while increased pressure under the right palm causes an increase in arpeggiation speed. When the right pad is not depressed, the notes of the current chord are voiced simultaneously. Additionally, the ACCORD features an LCD display. This shows the name of the current chord being voiced as well as the notes in that chord.
The control electronics are based on the MIOS platform modules. These modules are responsible for handling button input, MIDI I/O, and the LCD display. I built a four-voice analog synthesizer module based around the NTE864, which is a replacement for the old MAX8038, but with much greater temperature stability. I had difficulty with frequency drift so this part of the project never really got finished. Still, as a MIDI controller, the device is quite usable.