or 1/4') usually of III or more ranks=IV,IV-V,III-IV,V-VI. It contains octaves, major thirds (at least one), and fifths, though it can also contain the minor seventh. Rauschquint A harmonic mixture containing two or three or more(IV/V/VI/VII/VIII/IX/Rauschquint III-XII ranks of only octaves and fifths. Variables affecting tone color Mixture stops commonly include only unison and fifth pitch levels, though they sometimes include thirds and less commonly include other harmonics such as sevenths and ninths. The pedal division normally contains lower-pitched mixtures that reinforce the 16' fundamental. Manual mixtures with tierces can sound "disembodied" without a 16' stop being drawn with them. The frequency at which the various ranks in a mixture drop back by an interval (or break) as one ascends the compass determines to a great extent how the mixture sounds. If a mixture does not break, it is referred to as a harmonic mixture. Aristide Cavaillé-Coll built many examples of mixture stops labelled "Plein jeux harmonique". Some mixtures augment the treble in the lower ranges of the keyboard and the bass in the upper ranges of the keyboard. Mixture breaks 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. The "breaks" of a mixture involve the dropping out of a higher pitch at a given point within the keyboard's compass, and the addition of a lower pitch. This feature causes the mixture to sound relatively higher pitches in the lower parts of the keyboard, and relatively lower pitches towards the top end. It provides for definition in the bass and additional fundamental in the treble. 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. When that pitch is reached, it is usual practice to repeat the previous octave of pipes at the lower pitch level. Since mixtures commonly begin at pitches higher than 2′, octave repeats would be required as the pitches ascend. For example, here is the break structure of a typical Great Fourniture IV: Note Pitches on that note and above Fourniture IV-VII (St Jean De Luz Symphonie Hall) C#2 1-1/3' - 1’ - _2/3’ - 1/2’ C#14 2’ - 1-1/3' - 1’ - 2/3’ - 1/2' C#26 2-2/3' - 2’ -