Mixture (organ stop)

It is designed to be drawn with a combination of stops that forms a complete chorus, for example, principals of 8 foot (8′), 4′, and 2′ pitches.

Historically, the mixture descends from the medieval Blockwerk concept, an organ in which there were no stops and all the ranks sounded simultaneously.

A mixture exhibiting this trait is referred to as progressive, and is labeled with two numbers (e.g. Plein Jeu III-VII, Fourniture IV-VIII).

Sometimes a mixture is labeled with multiple numbers denoting the intervals above root pitch that it will sound.

Aristide Cavaillé-Coll built many examples of mixture stops labelled "Plein jeux harmonique".

The composition of pitches in a mixture will usually change (or break back) several times across the compass of the keyboard, often on subsequent C's, as in the example below.

Another reason for breaks, particularly in very high mixtures, is that builders find it impractical to make pipes smaller (higher) than the top of a 2′ rank, the C that's about 2/3″ long.