What Is A Fifth?
A fifth is the interval between two notes whose letter names are five alphabet
letters, or five lines and spaces, apart.
The note G is a fifth above C and the note F is a fifth below C.
Circle Diagram
In the circle of fifths diagram, the ascending circle of fifths moves
clockwise, while the descending circle of fifths moves counter-clockwise.
If you start at any point on the circle and go through 12 consecutive fifths,
you'll end up at the note you started from and will use all 12 chromatic
pitches in the process.
The order that sharps and flats occur in the key signature and the names of the
major and minor keys, in order of the increasing number of sharps or flats used
in the key signature, are based on the circle of fifths.
Ascending/Descending Fifths
C up to G is an ascending fifth in the circle of fifths. It can be written as
an ascending fifth, or its inversion, a descending fourth C down to G.
Similarly, C down to F is a descending fifth in the circle of fifths. It can be
written as either a descending fifth, or its inversion, an ascending fourth, C
up to F.
Major Sharp Key Names
Major sharp key names follow the ascending circle of fifths beginning with C
and continuing to C sharp. The key of C major has no sharps, the key of G major
has one sharp, the key of D major has two sharps, etc.
Major Flat Key Names
Major flat key names follow the descending circle of fifths beginning with C
and continuing to C flat. The key of C major has no flats, the key of F major
has one flat, the key of B flat major has two flats, etc.
Minor Sharp Key Names
Minor sharp key names follow the ascending circle of fifths beginning with A
and continuing to A sharp. The key of A minor has no sharps, the key of E minor
has one sharp, the key of B minor has two sharps, etc.
Minor Flat Key Names
Minor flat key names follow the descending circle of fifths beginning with A
and continuing to A flat. The key of A minor has no flats, the key of D minor
has one flat, the key of G minor has two flats, etc.
Order of Sharps
The order of sharps in the key signature follow the ascending circle of fifths
beginning with F sharp and continuing to B sharp.
Order of Flats
The order of flats in the key signature follow the descending circle of fifths
beginning with B flat and continuing to F flat.