Answer: The "haut" and "bas" (high and low) refer to soft instrument with the following musical characteristics:
"Haut" means loud, shrill and outdoor, while "Bas" refers to quieter and more intimate instrument.
Explanations:
Looking at Bas Instruments and Haut Instruments, Bas referred to soft instruments (literally, "low," but referring to volume, and not pitch) which were suitable for the chamber.
From as early as the 13 CE through the 15CE, there was a division of instruments into HAUT with this musical characteristics: (loud, shrill, outdoor instruments) and also BAS with these musical characteristics: (quieter, more intimate instruments).