Music Theory for Guitar - The Essential Basics

The Musical Alphabet

Music uses 12 notes that repeat in a cycle. On guitar, each fret is one half step (semitone):

The 12 notes (chromatic scale):
A → A#/Bb → B → C → C#/Db → D → D#/Eb → E → F → F#/Gb → G → G#/Ab → (back to A)

Important: No sharp/flat between B-C and E-F
These are "natural half steps"

Intervals: The DNA of Music

An interval is the distance between two notes. Everything in music — scales, chords, melodies — is built from intervals.

How Scales Are Built

A scale is a specific pattern of intervals. The major scale follows: W-W-H-W-W-W-H (W=whole step/2 frets, H=half step/1 fret):

C Major Scale:
C → D → E → F → G → A → B → C
  W   W   H   W   W   W   H

On the 5th string:
A|-3--5--7--8--10--12--14--15--|
   C  D  E  F  G   A   B   C

How Chords Are Built

Chords are built by stacking every other note from a scale (1st, 3rd, 5th):

C major scale: C D E F G A B
C major chord: C . E . G      (1-3-5)
D minor chord: D . F . A      (1-♭3-5)
G major chord: G . B . D      (1-3-5)

Why some chords are major, others minor?
Major 3rd (4 semitones) = major chord
Minor 3rd (3 semitones) = minor chord

Keys: Putting It All Together

A key is a group of notes and chords that sound good together. The key of C major uses only the white piano keys — no sharps or flats.

Next Steps

Dive deeper into intervals, explore keys, and learn the Circle of Fifths.