There are 42 intervals exclusive of the octave interval with ratio 1:2. There are seven seconds of three magnitudes, so determined in the genesis of notes - two in the ratio of 15:16; two, 9:10; and three, 8:9. There are seven corresponding sevenths - two in the ratio of 8:15; two, 5:9; and three. 9:16. There are seven thirds - one in the ratio of 27:32; three, 5:6; and three, 4:5; and there are seven corresponding sixths - three in the [Scientific Basis and Build of Music, page 109]
See Also
7.16 - Seventh
diminished seventh
dominant seventh
Major Seventh
Minor Seventh
seven
seven sevenths
seven thirds
seventh subdivision
Seventh
sharp seventh
six
sixth
top of the seventh octave