Organ builder breaks one mixture stop’s ranks across successive octave ranges

Evidence

Mixture stops have another important role to play in the synthesis pro­ cess. If a chromatic scale is played on a mixture stop alone, the scale would not be continuous and jumps in pitch would be heard at approximately every octave or twelfth, keeping the overall frequency span of the mixture much narrower than the five octave range of a manual. In this way, the mixture adds brilliance to the overall sound by enhancing high harmonics at the bass end of the keyboard, but these would become inaudible (and the pipe length would be too short to be practical) if continued to the treble. A mixture IV might consist of 19, 22, 26, 29 from C1 to C2; 15, 19, 22, 26 from C2 to C3; 12, 15, 19, 22 from C3 to C4; 8, 12, 15, 19 from C4 to C5; and 8, 12, 15, 15 from C5 to C6. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1606

Categorization

• DEFINE: Explains how a mixture stop’s broken ranks stepping down per octave keep high harmonics audible across the keyboard.