What is a musical interval?
A musical interval is the distance between exactly two pitches, measured in semitones, the pitch distance between two adjacent piano keys. Listen to this interval, expressed three ways, to hear the distinct demands each type makes on our ears: two notes one after the other are called a melodic interval, which can or , and a interval is when two notes are played at the same time.
Interval names have two parts. The ordinal counts letter names from the lower note to the upper one. The interval above spans C, D, and E, so we call it a third and its quality describes its exact size in semitones. Seconds, thirds, sixths, and sevenths each have a larger major and a smaller minor form. At four semitones, the interval above is a major third. Unisons, fourths, fifths, and octaves are called perfect, a label inherited from early tuning theory. Widening a perfect or major interval by a semitone makes it augmented, and narrowing a perfect or minor interval by a semitone makes it diminished.
Our ears' preferences have a physical basis. Two pitches an octave apart vibrate in a 2:1 frequency ratio, a perfect fifth is close to 3:2, and intervals built on simple ratios like these tend to sound smooth and stable. Intervals with more complex ratios that almost coincide but miss produce an audible beating and sound rough or tense. The conventional words for these sounds are consonant and dissonant, and the difference is easier heard than described. Compare this consonant with a dissonant .
Intervals that fit inside an octave are called simple intervals. There are thirteen simple intervals:
| Interval | ST. | Example | Listen |
|---|---|---|---|
| P1Perfect unison | 0 | “Jingle bells, jingle bells, jingle all …”Pierpont, “One Horse Open Sleigh” (1857) | |
| m2Minor second | 1 | The two-note Jaws motifJohn Williams, Jaws (1975) | |
| M2Major second | 2 | “Happy Birthday to you, happy …”“Happy Birthday to You,” traditional | |
| m3Minor third | 3 | “What child is this, who …”Set to “Greensleeves,” English traditional | |
| M3Major third | 4 | “Oh, when the saints, go …”“When the Saints Go Marching In,” gospel standard | |
| P4Perfect fourth | 5 | “Here comes the bride, all …”Wagner, “Bridal Chorus” from Lohengrin | |
| TTTritone | 6 | “The Simpsons”Danny Elfman, The Simpsons theme | |
| P5Perfect fifth | 7 | “Twinkle, twinkle, little star, how I …”“Twinkle, Twinkle, Little Star,” traditional | |
| m6Minor sixth | 8 | The alternating interval in “The Entertainer”Scott Joplin, “The Entertainer” (1902) | |
| M6Major sixth | 9 | “N - B - C”The NBC chimes | |
| m7Minor seventh | 10 | “There's a place for us, somewhere a …”Bernstein, “Somewhere” from West Side Story | |
| M7Major seventh | 11 | “Take on me, take me on, I'll be gone …”a-ha, “Take On Me” (1985) | |
| P8Perfect octave | 12 | “Somewhere over the rainbow, way …”Arlen & Harburg, “Over the Rainbow,” The Wizard of Oz |
Intervals past the first octave are called compound intervals. Compound intervals follow the same pattern and share the same notes with simple intervals: a ninth is the same as a second plus one octave, a tenth is equivalent to a third plus one octave, and so on. Intervals which share the same notes will have similar harmonic color and can be easy to confuse.
Simple intervals all have an inversion
If we transpose either note in a simple interval one octave, toward the other note, we can make a new interval using the same two notes. We call the resulting interval the inversion, and it will always be the same interval no matter which note we move. For instance, inverting the perfect fifth from will always result in a perfect fourth whether we transpose the or the .
An interval and its inversion always add up to twelve semitones, one octave, and their ordinals add up to nine. Fifths invert to fourths, thirds to sixths, seconds to sevenths, and a unison to an octave. When we invert an interval, we also flip the quality: major becomes minor, minor becomes major, augmented becomes diminished, and diminished becomes augmented. Perfect stays perfect. The tritone divides an octave exactly in half, so it inverts to itself, though in a literal sense, we're inverting a diminished fifth, resulting in an augmented fourth or vice versa.
Because the two members of an inverted pair share the same notes, it's easy to mistake an interval for its inversion.
Why do intervals matter?
Relative pitch is the ability to experience music through relationships: not which absolute notes are sounding, but the distance between notes relative to the other notes. That's why we generally use intervals as the unit of measurement in relative pitch. An interval keeps its identity no matter where it starts, and that's how a melody survives transposition into another key. A and a use different notes but are recognizable as the same musical interval.
Almost everything a musician does with relative pitch decomposes eventually into intervals. Recognizing a melody, taking dictation, harmonizing by ear, improvising over a progression all depend on hearing those relationships and how they fit into the key of the music.
Do interval reference songs actually work?
The internet's favorite method for learning intervals, commonly referred to as “mnemonics,” is to anchor each interval to a familiar melody. The is a minor second, opens with a perfect fourth, and starts with a perfect fifth. Still, advice about using mnemonics remains polarized. Some popular courses are built entirely on it, while others argue it fails in real music because we end up recalling a song rather than recognizing the interval.
The largest controlled test of song-anchoring is Reifinger (2012): 193 school-aged children received sixteen sessions of sight-singing instruction, with half of them being taught by relating tonal patterns to familiar songs. Both groups improved, but relating patterns to songs added no measurable advantage. A null result does not prove the method is ineffective, in fact it worked successfully, but it does falsify claims that reference songs are the best or only way to learn. The most recent synthesis of interval pedagogy (Kendüzler, 2026) recommends treating reference songs as scaffolding, useful for first contact with an interval and meant to be deliberately faded, so that the sound itself, not the song, ends up carrying the identification. Think of mnemonics as an optional beginner tool that is meant to be outgrown.
Intervals live inside a key
The strongest criticism of interval-only drilling is not that it fails but that it's incomplete. Intervals in real music are heard inside a tonal context, and the most recent synthesis of the pedagogy literature recommends combining contextual training, hearing intervals as positions relative to a tonal center, with isolated interval drilling (Kendüzler, 2026).
Scale-degree training and interval training are sometimes presented as rivals, but the two are not mutually exclusive. Both train pitch-relationship perception, and they occupy distinct spaces based on structural context. Interval training isolates the distance between two pitches without requiring a tonal center, while scale-degree training maps those same distances onto a tonic to encode harmonic function.
Relative listening is not just one strategy among several but the dominant mode of musical hearing for nearly everyone. Van Hedger & Bongiovanni (2023) found that listeners can make above-chance absolute tuning judgments about isolated notes and chords, but the moment relative pitch cues are present, as they are in virtually all music, absolute pitch judgments can collapse. Training intervals is training the channel our ears use most.
The science of ear training
Interval practice sits inside a well-studied field, auditory perceptual learning, and most of that field's landmark experiments were run on intervals and pure tones. Research has demonstrated that adults can improve measurably within days, short spaced sessions are more effective than long marathons, ideal training protocols increase difficulty progressively across specific dimensions, and transfer to new sounds arrives after learning trained ones. Our ear training hub includes detailed information about how these concepts map to ear training as a whole.