Bas referred to soft instruments (literally, "low," but referring to volume, not pitch) which were suitable for the chamber which included the vielle, rebec and other bowed strings, the lute and other plucked strings. Haut referred to loud instruments (literally "high" but referring to volume, not to pitch) which were suitable for outdoors which included the shawm, sackbut, pipe and tabor. Read the above history, facts and information about the Psaltery.

Definition and Description of the Psaltery
Definition and description of the Psaltery: The Psaltery can be described as a Medieval musical instrument which was a cross between a harp and a lyre. Description: a musical instrument, a kind of lyre or a harp with twelve strings, but having a trapezoidal sounding board under the strings. 

Family of Instruments: The Psaltery belongs to the family of String instruments.