How are scales, keys and modes built, and how do we recognise them by ear and on the page?
Construct and identify major, minor and modal scales, work out key signatures, and recognise tonality aurally.
How to build major, natural, harmonic and melodic minor scales and the common modes, derive key signatures from the circle of fifths, and identify tonality by ear for TASC Music Level 3.
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Building major and minor scales
Every diatonic scale is a fixed pattern of tones (T, a whole step) and semitones (S, a half step). The major scale pattern is T T S T T T S. Starting on C this gives C D E F G A B C, with no sharps or flats. Move the same pattern to G and you must raise the seventh note to keep the final T S, producing F sharp.
The minor scale has three working forms. Natural minor is T S T T S T T, so A natural minor is A B C D E F G A. Harmonic minor raises the seventh degree by a semitone, giving A B C D E F G sharp A, which creates the leading note needed for a strong perfect cadence. Melodic minor raises the sixth and seventh ascending (A B C D E F sharp G sharp A) and reverts to the natural form descending. Knowing which form is in use is a common exam task.
Key signatures and the circle of fifths
Key signatures collect the sharps or flats a key needs so you do not write them on every note. They follow the circle of fifths. Moving up a fifth adds one sharp: C, G (1 sharp), D (2), A (3), E (4), B (5). Moving down a fifth (or up a fourth) adds one flat: C, F (1 flat), B flat (2), E flat (3), A flat (4).
Sharps are added in the order F C G D A E B, and flats in the reverse order B E A D G C F. A quick check for sharp keys: the last sharp is the leading note, so the key is a semitone above it. For flat keys, the second-to-last flat names the major key.
Each major key shares its signature with a relative minor a minor third below. C major and A minor both have no sharps or flats; G major and E minor both have one sharp. To tell them apart you look at which note behaves as the tonic and whether the raised seventh of the minor appears as an accidental.
Modes
Modes are scales built by starting the white-note pattern on different degrees, and they appear often in jazz, folk and film music. The seven modes from C are Ionian (C, identical to major), Dorian (D, a minor scale with a raised sixth), Phrygian (E, minor with a flattened second), Lydian (F, major with a raised fourth), Mixolydian (G, major with a flattened seventh), Aeolian (A, identical to natural minor) and Locrian (B, rarely used). For analysis you describe a mode by comparing it to major or minor and naming the altered degree, for example "Dorian, a minor scale with a raised sixth".
Hearing tonality
Aural identification starts with the tonic chord. Play or sing back to the resting note, then decide whether the tonic triad sounds bright (major) or darker (minor). Listen for the leading note: a clear semitone push to the tonic suggests major or harmonic minor, while a whole-tone step below the tonic suggests a modal or natural-minor colour. A flattened seventh in a major-sounding tune points to Mixolydian; a raised fourth points to Lydian.
Putting it together
In both the written exam and aural tasks you move between three skills: constructing a scale from a pattern, deriving or naming a key signature, and judging tonality by ear. Practise writing each minor form from memory, drilling the circle of fifths in both directions, and singing tonic-to-leading-note to lock the sound of major against minor.
Exam-style practice questions
Practice questions written in the style of TASC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
TCE 20227 marksNotate, using accidentals rather than a key signature, an ascending E harmonic minor scale and a descending D melodic minor scale, then name the interval that gives harmonic minor its distinctive character.Show worked answer →
E harmonic minor ascending: E, F sharp, G, A, B, C, D sharp, E. Raise the seventh (D to D sharp) to form the leading note; everything else follows the natural minor.
D melodic minor descending: D, C natural, B flat, A, G, F, E, D. Descending, the raised sixth and seventh revert to natural minor, so C and B return to natural and flat.
Distinctive interval: between the lowered sixth (C) and raised seventh (D sharp) of E harmonic minor lies an augmented second of semitones, to . This gives the harmonic minor its tense, exotic colour. A common error is spelling it as a minor third (C to E flat); the size must stay a second, so the letter names must be adjacent.
TCE 20215 marksAn excerpt has two flats in its key signature and ends on a G minor chord with an F sharp accidental. State the key and justify your answer with two pieces of evidence from the score.Show worked answer →
The key is G minor. Two flats (B flat and E flat) belong to both B flat major and its relative minor, G minor, so the signature alone is not decisive.
Evidence one: the excerpt ends on a G minor chord, so G behaves as the tonic, not B flat. Evidence two: the F sharp accidental is the raised seventh (leading note) of G harmonic minor, which would not appear in B flat major.
For full marks, state both: "the music resolves to G minor and uses F sharp as a raised leading note, so it is G harmonic minor, not B flat major." Naming the key without justifying from the signature, final chord and accidental loses the explanation marks.