Audsley lists this stop with the following description: A stop, of 8 ft. pitch similar in form to, but smaller in scale than, the Viola. Its voice is intended to imitate hte tone of the muted Viola of the orchestra. If a very subdued intonation, combined with a slight modication of timbre, is desired, the pipes forming the stop may be conical in form: the scale giving the CC (8 ft.) pipe the diameter of 2 inches at the mouth line, and of 7/8 inch at top. Irwin also lists it, with the following description: A soft form of the Viola at 8' on the manuals, having only a suggestion of the harmonic structure of a String in its tone. Imitation of the muted instrument is accomplished by making the moderate-scaled pipes only very slightly conical, this being already a mild voice in its regular form. Narrowing the mouths is also a useful device in muting this stop. The Muted Viola is one of the must usable accompaniment stops, because its tone is pointed sufficiently by its String harmonics to escape being dull, and always remains definitive enough to hold up a solo stop like the Melodia, Oboe, Clarinet, or Gamba. It forms a rather dull céleste, but one that is useful on any division if tuned to a slow beat. The Muted 'Cello is a more interesting solo stop than this.
No examples of Muted Viola are known. Contributions welcome. Osiris contains a single example of Viola Sorda: