bichromatic

adjective4

1. •
   Of two colors.
2. •
   Describing a graph with edges of two possible colours.
3. •
   Describing a spectrometer (or similar instrument or system) capable of analysing two wavelengths at the same time.
4. •
   Employing or relating to a quarter tone scale.

   • Its title is "Musik mit Vierteltönen," and it contains the sum of the author's experiences with the "bichromatic harmonium" of his own construction. — 1922