...the sixth tone harmonium is a harmonium with three registers that's tuned very differently to your average twelve-tone equal temperament piano. The sound here is "very microtoney". The daddy of this is Alois Hába (1893-1973), a Czech composer who saw greater harmonic possibilities from expanding the reach of Western tonality, rather than the increased compositional complexity of twelve tone (as created by Arnold Schönberg).
Alois Hába
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