Fundamentals of Music Theory — Part 3: Scales, Key Signatures, and Modes

Pitch materials coalesce into recurring collections: major and minor scales,
diatonic modes, pentatonic and chromatic collections. Key signatures summarize the
accidentals that define these systems and the circle of fifths organizes
relationships among keys. This chapter explains how to construct common scales, how
to label scale degrees and sing them with solfège, and how to read and write key
signatures.

1) The major scale: pattern and purpose

The major scale is a seven-note step pattern of whole steps (W) and half steps (H):
W–W–H–W–W–W–H. Starting on C with all white keys yields C major; transposing the
pattern to any tonic (starting note) generates that key’s scale. The half steps
between 3–4 and 7–1 give the major collection its characteristic brightness and
stability at scale degrees ^1 (tonic), ^3 (mediant), and ^5 (dominant).

2) Scale degrees, solfège, and functional names

Scale degrees label each position relative to the tonic (^1 through ^7). They also
carry functional names: tonic (^1), supertonic (^2), mediant (^3), subdominant
(^4), dominant (^5), submediant (^6), leading tone (^7, a half step below tonic) or
subtonic (when a whole step below tonic, as in modal or natural minor contexts).
Movable-do solfège assigns syllables to each degree (do re mi fa sol la ti),
helping with sight-singing and hearing tendencies like ti rising to do, or fa
falling to mi.

3) Key signatures and the circle of fifths

A key signature places sharps or flats at the start of each staff line to signal
which notes are consistently raised or lowered. Sharp keys add sharps in the order
F, C, G, D, A, E, B; flat keys add flats B, E, A, D, G, C, F. The circle of fifths
orders keys by shared accidentals: moving clockwise adds a sharp (G, D, A, …),
anticlockwise adds a flat (F, B♭, E♭, …). Relative keys share a key signature (C
major and A minor); parallel keys share tonic but differ in quality (C major vs. C
minor).

4) Minor scales: three common forms

Natural minor uses the pattern W–H–W–W–H–W–W (half steps between 2–3 and 5–6).
Harmonic minor raises ^7 to create a leading tone and a strong dominant chord; this
introduces an augmented-second gap between ^6 and ^7. Melodic minor raises ^6 and
^7 ascending (to smooth the augmented second) and returns to natural minor
descending in traditional practice. These variations reflect competing goals:
melodic contour vs. harmonic function.

5) Spelling scales correctly

Each scale degree must use a distinct letter name in ascending or descending order.
In D major, the pattern requires F♯ and C♯, not G♭ or D♭. In A♭ major, use A♭, B♭,
D♭, E♭ rather than enharmonic sharps. Correct spelling ensures that stepwise motion
advances through adjacent letters and that chord-building by thirds yields properly
lettered stacks. It also aligns with the printed key signature, making sight-
reading predictable.

6) Identifying major or minor in context

To determine whether a passage is in major or minor, survey the key signature and
prominent scale degrees. A key signature alone is ambiguous (C major and A minor
have none). Look for raised ^7 (leading tone) or characteristic chords like V
(dominant) with a leading tone in minor. Melodic patterns (mi–fa–sol in major; la–
ti–do in minor) and cadence points often clarify. In ambiguous or modal music,
tonicization may shift, but recurring points of rest still stand out.

7) Modes: diatonic alternatives to major/minor

Modes are rotations of the diatonic collection with different half-step placements:
• Ionian (major): W–W–H–W–W–W–H.
• Dorian: W–H–W–W–W–H–W (minor with raised ^6).
• Phrygian: H–W–W–W–H–W–W (minor with lowered ^2).
• Lydian: W–W–W–H–W–W–H (major with raised ^4).
• Mixolydian: W–W–H–W–W–H–W (major with lowered ^7).
• Aeolian (natural minor): W–H–W–W–H–W–W.
• Locrian: H–W–W–H–W–W–W (diminished 5th above tonic).
Modal music may avoid leading-tone pulls, emphasizing different degrees (e.g., ♭VII
in Mixolydian).

8) Pentatonic and chromatic collections

Major pentatonic omits ^4 and ^7 (do re mi sol la), eliminating semitone friction
for a smooth, open sound common in folk and popular styles. Minor pentatonic (la do
re mi sol) is a mode of the major pentatonic. The chromatic scale uses all twelve
pitch classes, typically spelled with sharps ascending and flats descending for
readability, while preserving the rule of distinct letter names when feasible.

9) Practical skills: constructing and using keys

• Build major scales by the W–W–H–W–W–W–H template; memorize the circle of fifths
to predict key signatures.
• For minor, start from the relative major and adjust ^6/^7 for harmonic or melodic
needs.
• When transposing, maintain interval relationships: a melody’s step pattern should
remain intact in the new key.
• For reading, practice rapid key recognition: number of sharps or flats, tonic
location on staff, and accidentals common in that key.
• For improvisation, link scale degrees to harmony (e.g., emphasize ^3 and ^7 over
a V7 chord in tonal contexts).

10) Beyond keys: modulation and mixture (brief preview)

Modulation shifts tonic to a new key, often along the circle of fifths or through
shared-pitch collections. Modal mixture borrows from the parallel mode (e.g., ♭VI
or ♭III in a major key), enriching color while retaining the original tonic. These
topics become central in harmonic analysis, but even at the fundamentals stage,
recognizing borrowed tones and pivot chords deepens your sense of how scales and
keys generate musical variety.

Key terms recap: major scale, scale degrees, solfège (movable do), leading tone vs.
subtonic, key signature, order of sharps/flats, circle of fifths, relative vs.
parallel keys, natural/harmonic/melodic minor, diatonic modes (Ionian, Dorian,
Phrygian, Lydian, Mixolydian, Aeolian, Locrian), pentatonic, chromatic, modulation
(preview), mixture (preview).