Tropen

Musical term used by Josef Hauer for his own version of the system of twelve-note music. He divided the possible combinations of the 12 notes of the chromatic scale, which run into hundreds of millions, into 44 main groups, which he called Tropen. The Tropen were equivalent to keys in the diatonic system (consisting of the seven notes of any major or minor scale), and a change from one Trope to another is equivalent to modulation.

Hauer further divided each row of 12 notes into 2 halves of 6, which form 2 fundamental chords, whatever the order in which each 6 may appear.