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The seventh
The seventh is a distance of seven letters.
C(1) - D(2) - E(3) - F(4) - G(5) - A(6) - B(7)
C-B is a seventh, and D-C, or G-F, and also C-Bb, or D-C#, etc.
Types of seventh
The sevenh is an interval with a major. minor, diminished and augmented variation.
- Major seventh: five and a half tone. E.g. C-B, D-C#, Eb-D, F-E
- Minor seventh: five tones. E.g. C-Bb, D-Cb, Eb-Db, F-Eb
- Diminished seventh: four and a halve tones. E.g. C#-Bb, D#-C
- Augmented seventh: six whole tones. E.g. C-B#, Db-C#
Audio examples of the seventh
Respectively a major, minor, diminished and augmented seventh
Theorie vs reality
In "normal" - not theoratical - live, seconds, thirds and sixths are major or minor. The diminished and augmented versions are more theoretical. It's "normal" to ask a piano player to play a minor third, it is very uncommon to ask to play an augmented second.
The octave
The octave has also been discussed in the first part of this music theory course.
An octave is a distance of eight letters.
C-C' is an octave. The apostrophe at the second C indicates that the second C is an octave higher. The same way D-D' is an octave, And F#-F#', but also D-Db', G-G#', etc.
Types of octaves
The octave can be perfect, dimished or augmented. The same system as with all intervals applies.
A special one is the "double octave". A double octave has a distance of two octaves:
Audio examples of the octave
Respectively a perfect, diminished, augmented and double octave