I have always been fond of free reed instruments. In designing an ensemble that could be fixed in a tuning and that would feature simple enough instruments for students to join in the fun, Indian harmonium seemed the way to go: easy enough to tune, easy enough to play.
I designed the tuning with a series of compromises in mind. Free reeds are not particularly stable in pitch, so I went into this realizing any fine tuning would be more aspirational than practical. Also, a reed can’t be tuned terribly far in either direction without a fair bit of fussing. And, not having personally experienced free reeds in just intonation, I had my doubts about how any given tuning scheme would work out. In the end, I settled on a scheme that allowed for reeds to be tuned no more than 50 cents flat and 30 cents sharp. That decision eliminated, for example, the 13th partial, which falls right between those two boundaries.
I am very much attracted to working only in prime partials, up to very high limits. My piano is tuned that way, and I love it. But I hesitated to try that out with the harmoniums, especially if I had to cut several important partials out due to my tuning limitation. I’m currently fighting some wee hintings of regret that I didn’t just stick to my prime partials.
In the end, I have a system that allows for clouds of low-level consonances on various of the first 29 prime-numbered partials. It feels altogether too arbitrary and messy to me at the moment. I can see myself, in the future, ordering another two sets of reeds and tuning to a more elegant scheme, perhaps only on prime partials. But, for now, I made a decision, and I’ll live with it a while and see how it feels. I’m just starting out on this adventure and plan to continue it for the next thirty years or so – so I’m in no big hurry.