Diamond vibraphone

I constructed this instrument in early 2025. The layout and tuning is based on Harry Partch’s diamond marimba. This is a microtonal instrument in just intonation: all of the frequencies are based on relatively simple ratios. The layout is optimised for arpeggios: diagonals running north-east/south-west produce a major chord, while diagonals running north-west/south-east produce a minor chord.

I worked with Amanda Cole, a Sydney composer specialising in just intonation and Harry Partch, who composed a piece for the instrument. The piece was performed by Amanda’s Perfect Cents Ensemble, consisting of percussionist Jared Underwood, flautist Naomi Johnson, recorder virtuoso Alicia Crossley, and Amanda herself on lumatone.

See the performance on youtube:

This instrument is not strictly a vibraphone as it doesn’t have a motor, paddles or a sustain pedal, but the bars are tuned like a vibraphone and it has a similar range.

It is almost finished as of April 2025. See below for more photographs or watch a short clip on youtube:

The bars are made from 10mm aluminium flat bar stock. The front (bass) half of the vibraphone uses 50mm-wide bars. The back (treble) half of the vibraphone uses 32mm-wide bars. I used narrower bars for the back because the highest bars are fairly short – the shortest bar is 120mm. The beam theory I used only applies when the bars are much longer than they are wide, and I was worried that for a 50mm by 120mm bar, the 50mm wavelength would be close enough to interfere with the 120mm wavelength.

The harmonics are tuned to 1,4,10. To tune the harmonics, I used my Timoshenko beam theory implementation to generate curves for each bar:

Usually, one would use a bandsaw to roughly cut out the curve, then use a belt sander to clean it up. I don’t own a bandsaw, so I used a drill to remove most of the material:

The drilled bars are quite messy and are very rough approximations of the graph:

While sanding, I used my harmonic tuner to tune the overtones. None of the existing strobe tuner software that I found supported the diamond’s exotic tuning. The bars clean up nicely after enough sanding:

A video of a test bar in action:

More photographs of the almost-finished instrument: