A diminished seventh has three minor and three major seconds. C—B♭♭.
A minor seventh has two minor and four major seconds. C—B♭.
A major seventh has one minor and five major seconds. C—B.
192. An octave is an interval comprising seven seconds.
A diminished octave has three minor and four major seconds. C—C♭.
A perfect octave has two minor and five major seconds. C—C.
An augmented octave has one minor and six major seconds. C—C♯.
193. A ninth is usually treated as a second, a tenth as a third, etc. The interval of two octaves is often referred to as a fifteenth.
194. If the major diatonic scale be written and the interval between each tone and the key-tone noted, it will be observed that the intervals are all either major or perfect. See Fig. 64.
