A Cornet, or Jeu de Tierce, is a compound organ stop, containing multiple ranks of pipes. The individual ranks are most commonly of principal or flute tone quality. In combination, the ranks create a bright tone suggesting the Renaissance brass instrument, the cornett.
The Cornet is primarily used as a solo voice and the ranks of the Cornet follow the harmonic series; 8', 4', 2 2/3', 2', 1 3/5'. The 8' rank is stopped while the other ranks are open. The Cornet may contain from two ranks and up, though three, four, and especially five ranks are the most commonly found.
The two-rank version has only the 2 2/3' and 1 3/5' ranks, but this combination is more commonly called a Sesquialtera. The three-rank version has the 2 2/3', 2', and 1 3/5' ranks; the four-rank version adds the 4' rank. Some Cornets may include more harmonics, such as the seventh (1 1/7') and in rare cases the Ninth (8/9').