While geeking-out a little, we came across The Trichord by Steve Boyer.
“The Trichord is a keyboard instrument with keys arranged in a hexagonal pattern in order to emphasize harmonic relationships of 5ths and 3rds. The instrument is a keyboard with keys laid out in a hexagonal pattern. The relationship between the keys is such that triangles represent triads. An upward facing triangle is a major third and a downward facing triangle is a minor triad.” – Steve Boyer