Grove describes this stop as follows: A term probably derived from 16th-century French and Flemish usage to denote either the single mutation ranks (Octave, Quint, or Tierce) making up the Corneta or, more importantly, the chorus/solo Mixture; a kind of bass version of the treble Corneta, found over the centuries on most Iberian organs. Williams defines it as �a chorus or solo Mixture, usually a bass version of the treble Corneta Reale�. Sumner says �the Spanish nasardos is usually a quint mixture�. See Claron.
Osiris contains two dozen examples. Two (from the same organ) are single 2-2/3' ranks. The others are mixtures of II to V ranks. Examples whose composition is known are given below.