Nick Manoloff’s Modern Accompaniment Guide for Spanish Guitar.
M. &. Cole Publishing,
Volvelles like this one have been called the original computers since they aggregate a great deal of information. Turning the wheel allows one to change the chords in accordance with any key. The reverse gives the minor chords, accidentals and the definition of parallel minor chords and transpositions. Manoloff (1898-1969) was an inventor of steel tone bars for string instruments, a composer/arranger, and wrote other musical instruction books. If you buy Mr. Manoloff’s Book #1, the volvelle is free.
Collection of Ellen G. K. Rubin.