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The problem it solves
Scales, intervals and chords are all built by counting distances between notes. To do it confidently you need a reliable unit of measurement: the ruler of the whole system.
Detailed theory
Key idea
The semitone is the smallest distance; the octave divides into twelve equal ones. A tone is worth two.
On the piano, a semitone is two adjacent keys (counting the black ones); a tone leaves exactly one key in between.
Understand it
In the equal-tempered system we use today, the octave is split into twelve equal parts: twelve semitones. The semitone is therefore the smallest distance between two notes in the system, and every other distance is measured by adding semitones.
A tone is nothing more than two semitones in a row. That is why, when you later count intervals or build scales, you are simply adding tones and semitones: the tone and the semitone are the ruler that measures everything.
On the piano it is very clear: a semitone is two adjacent keys, counting the black ones too (for example C and C#). A tone is two keys with exactly one key in between (C and D, with C# in the middle). Watch out for one surprise: there are two places where two neighbouring white keys already form a semitone with no black key between them: E–F and B–C. The rest of the steps between neighbouring white keys (C–D, D–E, F–G, G–A, A–B) are tones.
Think of the semitone as the millimetre of the musical ruler: it is the finest mark you can make, and a tone is simply two marks apart. Just as you don’t measure a table with half a millimetre, in the equal-tempered system there is no step smaller than the semitone.
On the guitar the same idea is even more physical: each fret equals one semitone, so moving up one fret on a string raises the pitch by a semitone and moving up two raises it by a tone.
Staff & keyboard
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The two natural semitones on the keyboard: E–F and B–C. They are neighbouring white keys with no black one in between. Tap them to hear the smallest step.
How to recognise it
How it's written
There is no symbol of their own for the tone and the semitone: they are read as steps between neighbouring notes. On the piano, check whether the two keys are adjacent (semitone) or leave one in between (tone); on the guitar, count the frets: one fret is a semitone, two frets a tone.
How it feels
The semitone sounds like a small, close friction, two notes that almost touch; the tone sounds like a clean, slightly more open step. Sing E–F (semitone) and then C–D (tone) to feel the difference in width.
Common mistake
Assuming every step between neighbouring white keys is a tone: E–F and B–C are semitones, with no black key in between.
Forgetting to count the black keys when measuring a semitone: C–C# is a semitone even though one of the keys is black.
Try it
On the keyboard, play E–F and B–C (natural semitones) and compare them with C–D and F–G (tones): notice that the semitones are adjacent keys.
On the guitar, play an open string, then fret 1 (a semitone up) and fret 2 (a tone up) to hear the unit and its double.
On the instrument
Interval distance
E–F: a single semitone, and a natural one too, because there is no black key in between. It is the smallest distance in the system.
Interval distance
C–D: two semitones, that is a tone. Between C and D there is the C# key in the middle.
Songs that start with each interval
- Minor 2ndTauró (Jaws)
- Major 2ndGermà Jaume (Frère Jacques)
These famous song openings let you recognise a semitone versus a tone by ear: the Jaws motif is a semitone, while the start of Frère Jacques is a tone.
Where it's used
- Building scales
- Applying the pattern of tones and semitones to form a scale.
- Tuning
- Understanding micro-adjustments of pitch in terms of semitones.
- Measuring intervals
- Counting tones and semitones to tell whether an interval is major, minor or perfect.
Examples
Interval distance
C–C#: a semitone that does use a black key. Two adjacent keys are always a semitone.
Interval distance
F–G: a tone. Two white keys with F# in between add up to two semitones.
Exercises
Tell tone from semitone
Minor and major seconds by ear.
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0/8 answeredQuestion 1/8
What is the semitone in the equal-tempered system?