Notes and intervals
Semitone (half step)
A semitone, or half step, is the smallest interval in Western music: on the guitar it is the distance of one fret, and twelve of them make an octave.
What is a semitone?
A semitone (half step in American usage) is the smallest distance between two notes in Western music. On the guitar it is one fret: moving from the 5th to the 6th fret of the 6th string takes you from A to A#. Twelve semitones make an octave, and playing all of them in a row gives you the chromatic scale.
Two semitones make a whole step. On the neck, think in frets: 1 fret = 1 semitone, 2 frets = 1 whole step.
Where are the natural half steps?
Most neighbouring natural notes are a whole step apart, with an altered note in between: C, C#, D. Two pairs are only a semitone apart: E-F and B-C. That is why there is no black piano key between them.
You can see it on the open strings: the 6th string (E) gives F at the 1st fret, and the 2nd string (B) gives C at the 1st fret. Everywhere else, sharps and flats name the fret in between: the 1st fret of the 5th string is A# or B♭.
Counting intervals in semitones
Every interval has a fixed number of semitones, so a fixed number of frets on one string:
| Interval | Semitones | From C |
|---|---|---|
| Minor second | 1 | C to D♭ |
| Major second | 2 | C to D |
| Minor third | 3 | C to E♭ |
| Major third | 4 | C to E |
| Perfect fourth | 5 | C to F |
| Tritone | 6 | C to F# |
| Perfect fifth | 7 | C to G |
| Major sixth | 9 | C to A |
| Minor seventh | 10 | C to B♭ |
| Octave | 12 | C to C |
Check it on the 5th string: C at the 3rd fret, E at the 7th (4 frets), G at the 10th (7 frets).
Exercise: the one-finger-per-fret chromatic drill
Put your hand at the 5th fret, one finger per fret (index on 5, middle on 6, ring on 7, pinky on 8). Play frets 5, 6, 7, 8 on every string from the 6th to the 1st, then come back down. On the 6th string, say the notes out loud: A, A#, B, C.
Then use the semitone as an approach note: before each root, play the fret just below it. Before A (6th string, 5th fret), play G# at the 4th fret; before D (5th string, 5th fret), play C# at the 4th. That one-fret slide is the backbone of countless blues bass lines. In the guitar scales and chords tool, compare a major scale with the chromatic scale to see exactly where the half steps fall.
Key takeaways
- One semitone = one fret. Twelve semitones = one octave.
- E-F and B-C are the two natural half steps.
- Every interval is a number of semitones: 4 for a major third, 7 for a perfect fifth.
- The semitone creates the strongest pull: leading tone to tonic, approach notes.
Frequently asked questions
Is a half step the same as a semitone?
Yes. Half step is the American term and semitone the British one; both mean the same distance: one guitar fret, or two neighbouring keys on a piano.
How many semitones are in an octave?
Twelve. That is why the 12th fret of every string gives you the open-string note an octave higher. The twelve notes are C, C#, D, D#, E, F, F#, G, G#, A, A#, B.
Why does a semitone sound so tense?
Two notes a semitone apart rub hard against each other, and a note one semitone below another seems to want to move up to it. In C major, B (5th string, 2nd fret) pulls to C (3rd fret): that leading tone is what makes G7 resolve so strongly to C.
Related terms
Practise in the workshop
Take it from theory to the fretboard
Open the workshop tools and see this idea across the whole neck. Free account, no card needed.