Musical Intervals
An interval is the distance in pitch between two notes. Intervals are the fundamental building blocks of melody and harmony. Melodies are sequences of intervals. Chords are stacks of intervals. Understanding intervals gives you the vocabulary to describe, analyze, and create music with precision.
Every interval has two characteristics: a quantity (how many letter names span between the two notes) and a quality (whether the interval is major, minor, perfect, augmented, or diminished). The quality depends on the number of semitones between the notes within the letter-name span — equal temperament divides the octave into 12 of them.
The 12 Intervals Within an Octave
| Name | Abbreviation | Semitones | Example | Sound |
|---|---|---|---|---|
| Minor 2nd | m2 | 1 | C → Db | Dissonant, narrow |
| Major 2nd | M2 | 2 | C → D | Stepwise motion |
| Minor 3rd | m3 | 3 | C → Eb | Sad, minor quality |
| Major 3rd | M3 | 4 | C → E | Bright, major quality |
| Perfect 4th | P4 | 5 | C → F | Open, stable |
| Tritone | TT | 6 | C → F# | Unstable, tense |
| Perfect 5th | P5 | 7 | C → G | Open, consonant |
| Minor 6th | m6 | 8 | C → Ab | Expressive, somber |
| Major 6th | M6 | 9 | C → A | Warm, consonant |
| Minor 7th | m7 | 10 | C → Bb | Bluesy, dominant |
| Major 7th | M7 | 11 | C → B | Dreamy, longing |
| Octave | P8 | 12 | C → C | Perfect, complete |
How Intervals Are Named
Interval names combine a quality and a quantity. The quantity is the number of letter names spanned: C to E spans three letters (C, D, E) making it a 3rd. The quality depends on whether the interval is within the major scale of the bottom note. If both notes are in the major scale, the interval is either major or perfect. If the top note is lowered a semitone, it becomes minor or diminished. If raised, it becomes augmented.
Perfect intervals (unison, 4th, 5th, octave) can be perfect, augmented, or diminished — they never use major/minor. All other intervals (2nds, 3rds, 6ths, 7ths) use major/minor/ augmented/diminished. This naming system is universal and applies regardless of instrument.
Consonance and Dissonance
Intervals are categorized by how stable they sound. Consonant intervals (unison, 3rds, perfect 4th, perfect 5th, 6ths, octave) sound stable and pleasant. They form the basis of traditional harmony. Dissonant intervals (2nds, tritone, 7ths) create tension that demands resolution. The push and pull between consonance and dissonance is what gives music its emotional arc.
Context matters — a Perfect 4th can sound consonant in one setting and dissonant in another (especially when played against the bass note). The tritone was historically called diabolus in musica (the devil in music) for its unsettling sound, yet it's essential to the dominant 7th chord that drives Western harmony.
Interval Inversions
Inverting an interval means moving the lower note up an octave (or the higher note down an octave). The inversion changes both quality and quantity: major becomes minor, augmented becomes diminished, perfect stays perfect. The quantity is found by subtracting from 9. A Major 3rd (4 semitones) inverts to a Minor 6th (8 semitones). 3 + 6 = 9, Major ↔ Minor.
Understanding inversions helps you recognize intervals in different contexts. A m3 ascending is the same as a M6 descending. Recognizing this equivalence makes ear training easier — you can practice by checking whether the interval sounds like a 3rd or a 6th first, then determining the quality.
Compound Intervals
Intervals larger than an octave are called compound intervals. A 9th is an octave plus a 2nd (14 semitones total). A 10th is an octave plus a 3rd. Compound intervals have the same harmonic quality as their simple counterparts — a 9th functions like a 2nd but with more space between the notes. They're common in chord extensions (Cmaj9 includes a Major 9th) and piano voicings.
Practice With Our Interval Trainer
The best way to learn intervals is through focused ear training. Our Interactive Interval Trainer plays random intervals and tests your recognition. Start with just the easiest intervals (P5, P8, M3) and gradually add more. Use reference songs to anchor each interval in your memory. Ten minutes of daily practice will dramatically improve your recognition over several weeks. You can also apply interval knowledge to chord construction and scale building — all of which use the same interval framework.