Music theory
Music intervals: how to name them and hear them
An interval is the distance between two notes, named by two things at once: how many letter names it spans and how many half steps it contains. C to E spans three letters and four half steps — a major third. Change either number and the name changes. Learning intervals means learning to do that in both directions: from the page and from the sound.
Intervals on the guitar, where the shape does the counting
On a fretboard, an interval is a shape, and the same shape means the same interval anywhere on the neck. That makes the guitar the fastest instrument for learning them by feel.
From any note on the low E or A string: same fret, next string up is a perfect fourth (except between G and B strings, where it is a major third). Two frets up, next string is a perfect fifth. Same fret, two strings up is a minor seventh; one fret higher makes it major.
The exception at the G–B string pair is the one thing to memorise: the tuning shifts by a half step there, so every shape crossing it moves by one fret.
Play a fifth, then a fourth, then a third from the same root, and the difference stops being arithmetic within a few minutes.
Recognising intervals by song
The traditional method, and it works because the ear stores tunes better than distances. Each interval gets a song whose first two notes contain it:
Minor second — the Jaws theme. Major second — «Happy Birthday». Minor third — «Greensleeves». Major third — «When the Saints Go Marching In». Perfect fourth — «Here Comes the Bride». Tritone — «The Simpsons». Perfect fifth — «Twinkle, Twinkle». Major sixth — the NBC chime. Minor seventh — the «Star Trek» theme. Octave — «Somewhere Over the Rainbow».
Choose songs you actually know rather than the canonical ones — the method depends on instant recall, and a reference you have to think about is no reference at all.
Practise descending separately. Most people can name a rising fifth long before they can name a falling one, because the songs they learned were all ascending.
How intervals are named
The number comes from counting letter names inclusively: C to G is C, D, E, F, G — five letters, so a fifth.
The quality comes from the half steps. Unisons, fourths, fifths and octaves are perfect; seconds, thirds, sixths and sevenths are major or minor. Shrink a minor or a perfect interval by a half step and it becomes diminished; expand a major or perfect one and it becomes augmented.
The tritone — three whole tones — is the awkward case with two names: an augmented fourth or a diminished fifth, depending on how it is spelled. Both sound identical and both are exactly half an octave.
Why intervals matter beyond naming them
Chords are stacked intervals: a major triad is a major third with a minor third on top, a minor triad reverses them. Hearing the third tells you the chord's quality before you identify the chord.
Melodies are chains of intervals, and a melody transposed keeps them all — which is why a tune is recognisable in any key. This is also the basis of movable-do solfege, where the syllable names the relationship.
In tuning and harmony, the perfect fifth is the strongest relationship after the octave, and the circle of fifths is what happens when you follow it repeatedly.
A practice routine that works
Five minutes, three parts. Play a note, sing the interval you are aiming for, then check it. Singing before checking is what builds recognition — playing both notes first teaches nothing but comparison.
Then reverse: have something play two notes and name what you heard. Ear-training tools do this, and so does a friend at a keyboard.
Finally, find the interval in music you are already playing. Naming the leap at the start of a song you know attaches the label to something the ear already holds, and that association survives long after drills are forgotten.
Common questions
What is an interval in music?
The distance between two notes, named by how many letter names it spans and how many half steps it contains. C to E spans three letters and four half steps, which makes it a major third.
How do I identify intervals by ear?
Attach each one to the first two notes of a song you know instantly — a fifth to «Twinkle, Twinkle», a fourth to «Here Comes the Bride», an octave to «Over the Rainbow». Practise descending intervals separately, since the familiar references are all ascending.
How do intervals work on guitar?
As shapes that stay the same anywhere on the neck: same fret one string up is a fourth, two frets up one string is a fifth. The exception is the G to B string pair, where the tuning shifts by a half step and every crossing shape moves one fret.
What is a perfect fifth?
An interval of seven half steps spanning five letter names — C to G. After the octave it is the strongest relationship between two notes, which is why power chords use it and why the circle of fifths exists.
Why are some intervals called perfect?
Unisons, fourths, fifths and octaves have one basic form and are called perfect; seconds, thirds, sixths and sevenths come in major and minor versions. The naming is inherited from medieval theory about which intervals counted as stable.
What is a tritone?
Three whole tones — exactly half an octave. It is spelled either as an augmented fourth or a diminished fifth depending on context, and both spellings sound the same.
Sing it, then check it
Play a note in the studio, sing the interval you are aiming for, and see whether you landed. Checking after singing is what builds recognition; checking before it only builds comparison.