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The problem it solves
The major scale is the reference frame for most tonal music: melody, key and diatonic chords all rest on it. To build it from any note you need to know its exact formula.
Detailed theory
Key idea
The major scale always follows the pattern tone-tone-semitone-tone-tone-tone-semitone (T-T-S-T-T-T-S).
The only two semitones fall between degrees 3 and 4 and between degrees 7 and 8; every other step is a tone.
Understand it
A major scale is seven ordered notes plus the repetition of the first at the octave. What defines it is not the actual notes but the succession of distances between them: tone, tone, semitone, tone, tone, tone, semitone. This pattern is the major-scale formula and it never changes.
The two semitones of the pattern always sit in the same place: one between the third and fourth degree, the other between the seventh degree and the tonic above (degree 8). In C major this is effortless to see: the natural semitones E-F and B-C fall exactly between degrees 3-4 and 7-8, which is why C major uses only the white keys: C D E F G A B C.
Since the pattern is identical from any note, when you change tonic you must adjust some notes with sharps or flats so the semitones keep falling on degrees 3-4 and 7-8. For example, G major needs an F#: that way the step from the seventh degree to the tonic (F#-G) stays a semitone, just as the formula demands.
Think of the formula as the template of a railing: the bars are always spaced with the same sequence of wide gaps (tones) and narrow ones (semitones). You can set the template down wherever you like; as long as you respect the gaps, you always get a major scale, just in another spot on the keyboard.
That is why the major scale is the reference frame of tonal music: it fixes the degrees, gives the basis of the key and determines which diatonic chords live in it. Mastering its formula is what lets you transpose and recognise it everywhere.
Staff & keyboard
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The two semitones of the major pattern in C: E-F (degrees 3-4) and B-C (degrees 7-8). The rest of the steps are tones.
How to recognise it
How it's written
Read the scale as a sequence of steps between neighbouring notes: see where the semitones are (degrees 3-4 and 7-8) and check that the rest of the steps are tones. On the keyboard, in C major it shows at once because the semitones coincide with the neighbouring white keys E-F and B-C.
How it feels
Sing or play the whole scale from bottom to top: you will feel a stable, bright path that culminates when the seventh degree, very close to the tonic, resolves onto it. That narrow final step is the 7-8 semitone, the audible mark of the major pattern.
Common mistake
Thinking every step of the major scale is a tone: there are two that are semitones, between degrees 3-4 and 7-8.
Trying to apply the pattern from another tonic without adding the necessary sharps or flats; without them the semitones fall in the wrong place and it stops being a major scale.
Try it
On the keyboard, play C D E F G A B C, noticing that the narrow steps (semitones) fall on E-F and B-C; the rest are tones.
Apply the formula T-T-S-T-T-T-S from G and check that you need an F# so the 7-8 semitone (F#-G) is preserved.
On the instrument
Staff & keyboard
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The whole C major scale: only white keys. The tonic C opens and closes the scale at the octave.
Interval distance
E-F: the semitone between the 3rd and 4th degree of C major. It is one of the two narrow steps of the pattern.
Interval distance
C-D: the tone between the 1st and 2nd degree. Most steps of the major pattern are tones like this one.
The scale and its steps
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The major pattern T-T-S-T-T-T-S on the keyboard: each arrow marks whether the step is a tone or a semitone. Switch scales and check the pattern never moves.
Where it's used
- Transposing
- Applying the pattern T-T-S-T-T-T-S to build the same major scale from any note.
- Understanding key signatures
- Working out which sharps or flats each key needs to keep the semitones on degrees 3-4 and 7-8.
- Recognising the key
- Hearing which tonic the major pattern leads to in a melody or song.
Examples
Staff & keyboard
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G major: the same pattern T-T-S-T-T-T-S, now with F# so the 7-8 semitone (F#-G) is preserved.
Mini test
Check that you've got it.
0/10 answeredQuestion 1/10
What is the tone-and-semitone pattern of the major scale?