A Mixture consisting of a Twelfth and a Fifteenth. Wedgwood says �so named in contradistinction to Sharp Mixture, on account of the grave or full effect imparted by the Twelfth rank.� Irwin says: �[2' + 2-2/3'], sometimes called a Grave Mixture, is probably the oldest pitch combination known in a compound stop.� That may be true, but the earliest known use of the name Grave Mixture dates from 1877 (see below). Earlier names for this combination of pitches include Doublette and Rauschquinte. Irwin also mentions a 2-rank Grave with no description; we assume it to be a synonym.
Osiris contains 12 examples; seven are of two ranks, three of which are known to be 2' + 2-2/3' (the compositions of the other four are unknown). Four are of three ranks, and one of four ranks.