Keys and Key Signatures | Ukulelearn lessons

A key is a home base. It tells you which seven notes are in play, which chord feels like resolution, and why certain chord progressions work so consistently across thousands of songs.

What Is a Key?

When you say a song is in C major, you're saying that the note C feels like "home" - the resting point. The other notes in C major (D, E, F, G, A, B) create varying degrees of tension that pull back toward C. That pull-and-release is what makes music feel like it goes somewhere.

Every major key has exactly seven notes, arranged with the same pattern of whole and half steps. Change the starting note and you get a different key - but the pattern stays the same.

The Major Scale Pattern

The major scale follows this pattern of whole (W) and half (H) steps:

W-W-H-W-W-W-H

Starting on C: C (W) D (W) E (H) F (W) G (W) A (W) B (H) C.

Starting on G: G (W) A (W) B (H) C (W) D (W) E (W) F# (H) G. The F# is required to maintain the pattern.

Key Signatures and Sharps/Flats

Each key requires specific sharps or flats to keep its interval pattern intact. C major needs none. G major needs one sharp (F#). D major needs two (F# and C#). F major needs one flat (Bb).

For practical playing, start with the keys most common on ukulele: C, G, F, D, and A. These cover the majority of songs you'll encounter.

Chords in a Key

Each note in a key generates a chord when you stack thirds above it. In C major:

C - C major (I)
D - D minor (ii)
E - E minor (iii)
F - F major (IV)
G - G major (V)
A - A minor (vi)
B - B diminished (vii°)

The I-IV-V-I progression appears in thousands of songs precisely because these chords share notes and create natural tension and resolution. Am (the vi chord) is the "relative minor" - it uses the same notes as C major but centers on A instead.

Finding the Key of a Song

Listen for the chord that sounds most settled - the one where the music could comfortably stop. That's usually the I chord. If the song uses C, F, and G mostly, you're in C major. If it uses Am, F, C, and G, you're likely in C major but emphasizing the vi chord.

Practice Exercise

Play C, F, and G chords on your ukulele and end on C. Listen to how C feels like the finish line. Now play the same chords but end on G. Notice the tension - G wants to resolve back to C. Play with that feeling: leave the phrase on G, wait a second, then resolve to C. That's the dominant-to-tonic pull working in real time.

Questions and Answers

What does it mean for a song to be in a key?: A song in a key uses a specific set of seven notes built from a major or minor scale. One note acts as the tonal center (home base), and the other notes create varying degrees of tension and resolution around it. The key determines which chords naturally fit the song.
How many sharps or flats does C major have?: C major has no sharps or flats. It uses only the natural notes C, D, E, F, G, A, and B. This makes it the simplest key to understand theoretically and a good starting point for learning music theory on any instrument.

Next up: How Chords Are Built - using intervals and scale knowledge to understand why chord shapes are what they are.