A Dictionary of Music and Musicians/Mixture
MIXTURE. An organ stop ordinarily furnished with from two to five comparatively small pipes to each key. It is compounded of the higher-sounding and therefore shorter members of the 'foundation' and 'mutation' classes of stops, combined or 'mixed,' and arranged to draw together, as they, practically, are seldom required to be used separately. The Mixture represents or corroborates the higher consonant harmonic sounds suggested by nature, and in the bass produces tones to the third or fourth octave above the unison or chief foundation tone. As the musical scale ascends, the higher harmonics become weak and inaudible to the ear; hence in a Mixture stop it is customary to discontinue the higher ranks as they ascend, one or more at a time, and insert in lieu a rank of lower tone than was previously in the stop, but appearing as a separate stop. This alteration is called a 'break.' These return-ranks serve the best of purposes. In a Pianoforte it is well known that the strings increase in number from one in the bass to two higher up, and afterwards to three, to preserve an evenness in the tone. In a similar manner the return-ranks, when well managed, considerably reinforce the strength of the treble part of the organ. [Mutation.]
[ E. J. H. ]