lesson
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In 1722, Johann Sebastian Bach published a landmark collection of 24 preludes and fugues called The Well-Tempered Clavier to prove that keyboard instruments could finally play in every single key without sounding wildly out of tune.
To analyze and write Bach chorales, you need instant mastery over every key signatureβnot just the simple ones, but all the way to seven sharps, seven flats, and even theoretical keys with double accidentals.
How do 12 musical pitches generate all of these distinct tonal worlds?
The Circle of Fifths and Accidental Order
A key signature is the set of sharp or flat symbols placed on the staff at the start of a piece that tells you which notes are raised or lowered throughout.
Every time you move up a perfect fifth (7 semitones), you add one sharp; every time you move down a perfect fifth (or up a perfect fourth), you add one flat.
πInteractive diagram
The order of sharps is always Fβ― β Cβ― β Gβ― β Dβ― β Aβ― β Eβ― β Bβ― (often memorized as Father Charles Goes Down And Ends Battle).
The order of flats is the exact reverse: Bβ β Eβ β Aβ β Dβ β Gβ β Cβ β Fβ (Battle Ends And Down Goes Charles' Father).
Once you know the order of accidentals, how do you instantly identify the tonic note in both major and minor modes?
Reading Sharp and Flat Keys
For sharp major keys, the last sharp is always the leading tone (7^), which sits a minor second (one half step) below the tonic (1^).
For flat major keys, the penultimate flat (the second-to-last flat) is the tonic name itself; with only one flat (Bβ), the major key is simply F major.