A mutation stop of 2-2/3' in the manuals and 5-1/3' in the pedal. It represents the lowest non-unison pitch that reinforces a harmonic of the fundamental pitch (8' on the manuals, 16' on the pedals). As such, it is the most important mutation pitch. While these names have been used as synonyms for Twelfth, particularly in Germany, they more properly denote a stop of flute tone. Many forms have been used, including open, stopped, chimneyed, and conical. The Nasard of the classical French organ is indispensable for proper registration of its literature. This Nasard is usually stopped or chimneyed in the bass, and open or conical in the treble. Bedos specifies six different scales: wide (for the Grand Orgue) and narrow (for the Positif) for open pipes (Nasard Ouvert), tapered pipes (Nasard à Fuseau), and chimneyed pipes (Nasard en Cheminée). He states that tapered pipes are rarely used except for the treble of the Nasard when its bass has chimneys, and that this treatment is rather common in Positif divisions. On the theatre organ, the 2-2/3' pitch is taken from the Tibia Clausa or Concert Flute. Williams dates these names from the 1530's. They may trace their origin to the German word nase, meaning �nose�, and referring to the nasal character imparted by these stops; a more likely origin is the German word nach, meaning �behind�, and referring to ranks of pipes place between the case pipes and the Hintersatz of a separated Blockwerk. According to Grove, early uses of these names referred to a registration or effect rather than a rank of pipes. Wedgwood claims that these names are occasionally synonymous with Rauschquinte. Adlung claims that Nasat is not always a fifth-sounding stop, but the only example he cites is �Assat 2' at Hildesheim�.