2.3 Circle of Fifths & Transposition

The circle of fifths

The circle of fifths arranges keys by ascending 5ths: C–G–D–A–E–B… Each step clockwise adds a sharp; counterclockwise (by 4ths) adds a flat. It maps every key signature.

Finding the key

For sharp keys, the last sharp is the leading tone — go up a half step to find the tonic. For flat keys, the second-to-last flat names the key (except F major).

Transposition

Transposition rewrites music at a different pitch level, keeping all intervals the same. Transposing instruments (like the B♭ clarinet) sound a different pitch than written.

Key terms

Circle of fifths

keys by ascending 5ths: C-G-D-A-E-B...

Clockwise / counterclockwise

adds sharps / adds flats

Sharp-key tonic

a half step above the last sharp

Flat-key tonic

the second-to-last flat (except F major)

Transposition

shift pitch level, keep intervals identical

Try an AP-style question

Moving clockwise on the circle of fifths…

1. removes all sharps
2. changes to minor
3. adds one sharp each step
4. adds one flat each step