Lesson 4: Keys and Key Signatures
A scale is a set of notes. A key is what you get when a piece of music treats one of those scales as home base - every melody and chord in the piece is heard in relation to that scale's tonic. When someone says a song is 'in the key of C major,' they mean the C major scale is that song's home.
Every key has a key signature - a fixed set of sharps or flats that belong to it, coming directly from its scale's own formula. C major happens to have none at all, which is exactly why it's usually the first key musicians learn: every note is a plain white key on a piano, with no sharps or flats to keep track of.
Related to C Major
The major key built on C, using the notes of the C major scale.
- parallel: C Minor (key)
- relative: A Minor (key)
- frequently used with: Primary (Cadential) Progression (progression)
- frequently used with: Jazz Turnaround (ii-V-I) (progression)
- frequently used with: Pop Progression (I-V-vi-IV) (progression)
- frequently used with: Pop Progression, Alternate Rotation (vi-IV-I-V) (progression)
- frequently used with: 50s Progression (I-vi-IV-V) (progression)
- frequently used with: 12-Bar Blues (progression)
- frequently used with: Extended Jazz Turnaround (progression)
- frequently used with: Pop Progression, Alternate Rotation (I-IV-vi-V) (progression)
Every major key has a relative minor - a minor key built on the major scale's 6th degree, using the exact same seven notes and the exact same key signature, just centered on a different tonic. Relative keys sound related because they share all the same notes; they just feel different because the ear hears a different note as home.
Related to A Minor
The natural minor key built on A, using the notes of the A natural minor scale.
- relative: C Major (key)
- parallel: A Major (key)
- frequently used with: Harmonic Minor Cadential Progression (i-iv-V) (progression)
- frequently used with: Andalusian Cadence (i-VII-VI-V) (progression)
- frequently used with: Minor Primary Progression (i-iv-v) (progression)
- frequently used with: Natural Minor Loop (i-VI-III-VII) (progression)
Don't confuse relative with parallel. Relative keys (like C Major and A Minor) share the same notes but a different tonic. Parallel keys (like C Major and C Minor) share the same tonic but different notes. Both are real relationships between keys - they just mean different things.
Which key is the relative minor of C Major?
What do relative keys (like C Major and A Minor) share?
You've now covered the two ways a piece of music organizes pitch: a scale gives you the raw notes, and a key tells you which of those notes counts as home. Next: stack notes from a scale on top of each other, and you get chords.