Echo Vox Humana is mentioned only by Irwin, who says: A soft Reed stop of 8' manual pitch, similar in tone to the Vox Humana, but more muffled and softer. This stop is sometimes labelled Vox Mystica. It may be placed in an inner swell box for additional softness. It sounds as just a whisper of extremely high overtones. Its tenuous, soft timbre is most effective in chords near the middle of the keyboard. Here it may seem to give no sense of pitch at all. Stilles Regal is listed only by Sumner, who describes it only as: �8 ft. and 4 ft. A quiet vox humana.� With such as description, we consider it to be a synonym for Echo Vox Humana. The German word stilles means �quiet�.
None known for either name.