A small-scaled principal-string hybrid of soft tone, made from pipes rich in tin. When placed staccato, its tones may resemble those of the orchestral harp, hence the name Harfenprinzipal. According to Maclean it is often conical in form. While Irwin reports that it is found at 8' and 4' pitch, the only known examples are at 16' and 8'. The Harfenprincipal was known to Praetorius (c.1600). Adlung writes: �I really do not know what it might be. ... to surmise: stops like this refer to David's harp, whose rather twanging tone it has finally been possible to imitate.� To which the translator (Faulker) adds the following footnote: �the percussive speech of various narrow-scaled string stops, notably the Violdigamba ... were still relatively recent developments in the organ at the time Adlung was writing this treatise.�
No examples of Echo Geigen or its variants are known. Contributions welcome.