Audsley lists Kleinprinzipal with the following description: The term which has occadionally been employed to designate the Octave, 4 ft., of pure organ-tone, the scale of which is adjusted from that of the Majorprinzipal, 8 ft. This octave stop is identical with the old English Principal, 4 ft., and the Halbprinzipal of the old German organ-builders. Irwin also lists it with a slightly different view: A Foundation stop of 4' on the manuals, having in almost all examples the tone quality of a small-scale Octave, but not so soft as an Echo Diapason 4'.
Klein Principal 1', Positif; West End United Methodist Church, Nashville, Tennessee, USA; Moeller 1983.