Intervals
What Are Intervals?
An interval is the distance between two pitches, measured by:
- Semitones (half steps)
- Letter names (scale degrees)
Intervals can be:
- Melodic: Played sequentially (e.g., C → D in a melody).
- Harmonic: Played simultaneously (e.g., C and E in a chord).
Types of Intervals
1. By Size
| Interval Name | Semitones | Example (C as root) | Quality |
|---|---|---|---|
| Unison | 0 | C → C | Perfect |
| Minor Second | 1 | C → D♭ | Diminished |
| Major Second | 2 | C → D | Major |
| Minor Third | 3 | C → E♭ | Minor |
| Major Third | 4 | C → E | Major |
| Perfect Fourth | 5 | C → F | Perfect |
| Tritone | 6 | C → F♯/G♭ | Augmented/Diminished |
| Perfect Fifth | 7 | C → G | Perfect |
| Minor Sixth | 8 | C → A♭ | Minor |
| Major Sixth | 9 | C → A | Major |
| Minor Seventh | 10 | C → B♭ | Minor |
| Major Seventh | 11 | C → B | Major |
| Octave | 12 | C → C′ | Perfect |
2. By Complexity
- Simple Intervals: Span ≤ 1 octave (e.g., major third).
- Compound Intervals: Span > 1 octave (e.g., major 10th = octave + major third).
Interval Qualities
- Perfect: Unison, 4th, 5th, octave (stable, consonant).
- Major/Minor: 2nds, 3rds, 6ths, 7ths (major = brighter, minor = darker).
- Augmented/Diminished: Altered by a semitone (e.g., C→F♯ = augmented 4th; C→G♭ = diminished 5th).
Consonant vs. Dissonant Intervals
| Consonant (Stable) | Dissonant (Unstable) |
|---|---|
| Perfect Unison, 4th, 5th, octave | Minor 2nd, Major 7th |
| Major/Minor 3rd, 6th | Tritone (augmented 4th/diminished 5th) |
| Major 2nd, Minor 7th |
Note: Context matters! In jazz, dissonance (e.g., tritones) is embraced for tension; in classical, it often resolves.
Enharmonic Intervals
Same semitones, different names:
- C→F♯ = augmented 4th (6 semitones).
- C→G♭ = diminished 5th (6 semitones).
Key Applications
- Melodies:
- Steps (e.g., C→D = major 2nd) create smooth motion.
- Leaps (e.g., C→E = major 3rd) add drama.
- Chords:
- Major/minor triads = root + 3rd + 5th.
- Dominant 7th chords = root + 3rd + 5th + minor 7th.
- Harmony:
- Perfect 5ths anchor cadences (e.g., V→I).
- Tritones resolve inward (e.g., B→F resolves to C→E).
Interval Inversions
Flip the notes to create a new interval:
- Major 3rd (C→E) → Minor 6th (E→C).
- Perfect 4th (C→F) → Perfect 5th (F→C).