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What are musical intervals, hearing every one
A musical interval is the distance between two notes. That distance is measured in semitones — the smallest step on a piano, from one key to the very next, black or white — and it gets a name made of a number (second, third, fifth…) and a quality (major, minor, perfect). It is the intervals, not the notes, that make a melody sound the way it does: the same string of distances, started from any note, is the same tune. Below, each of those ideas is a toy: drag it, listen, and watch the name change before you read a word about it.
Scroll and play — everything on this page makes sound when you touch it.
Distance: how far one note is from another
Drag the handle along the keyboard and listen: the lower note stays put, the upper one moves away, and the gap between them is the interval. Every neighbouring key — black or white, it makes no difference — is one semitone, also called a half step: the smallest distance the piano has. Two semitones make a whole tone.
Counting semitones is the most exact way to measure an interval, and it is what the ear does without knowing: seven semitones sound like seven semitones from any starting key. But nobody says "seven semitones" in a lesson — they say "perfect fifth". The next two sections explain where that name comes from: first the number, then the quality.
Drag the handle along the keyboard and watch the semitone count and the interval name change with every key.
The number: count the letters, first to last
An interval's number comes from counting letter names from the first note to the last, both ends included. From C to G: C, D, E, F, G — five letters on your fingers, so it is a fifth. C to E is three letters, a third; C to the next C is eight, an octave.
This is where nearly everyone trips: five notes counted is four steps taken. Because the count includes the note you start on, the number is always one more than the number of steps climbed — and C to the same C, going nowhere, is not "zero" but a unison, the interval numbered one. Notice too that the black keys play no part in this: the number counts letters only.
Move the upper note with ▲ and ▼ and follow the letter count: every step adds one.
Major and minor: same number, two sizes
Pick the third and switch between major and minor: the number has not changed — it is still three letters counted — but the size has. A major third is four semitones; a minor third, three. One semitone of difference, and the ear hears it at once: two different intervals sharing one number.
Seconds, thirds, sixths and sevenths all come in these two sizes, and the quality is what completes the name: "major third", not just "third". Many people hear the major as brighter or happier and the minor as darker or sadder — a useful first clue, not a rule: the same minor third can sound sweet or dramatic depending on the music around it. What counts is training the ear to recognise the size.
Choose the number, switch between major and minor and listen: the difference is a single semitone.
One after the other, or both at once
The same two notes can sound in two ways: one after the other, as in a melody, or at the same time, as in a chord. The first is a melodic interval; the second, a harmonic one. Play it both ways and notice: same distance, same name, and quite a different feeling.
In sequence, the ear follows the leap — that is how you perceive the shape of a melody. Together, the two notes blend into a single sound, and what you hear is the colour of the blend: smooth or rough, full or hollow. That is why every interval needs training both ways: recognising the leap and recognising the blend are sister skills, not the same one.
Play the same two notes "one after the other" and then "together", and listen to what changes when nothing has changed.
Smooth or rough: consonance, dissonance and the perfect intervals
Turn the dial through the twelve intervals and watch the meter: some sound smooth, as if the two notes melted into one; others sound rough, with friction, as if they wanted to move on. Smooth is called consonance; rough, dissonance. Neither is a mistake — music lives on the journey between them, and dissonance is precisely what creates the tension that consonance resolves.
The fourth, the fifth and the octave (and the unison) are a case apart: they do not come in major and minor, and so they are called perfect — perfect fifth, perfect octave. Stretch the fourth by a semitone, or shrink the fifth by one, and you land on the same thing: six semitones, exactly half an octave. That interval has a name of its own, the tritone, and it is among the roughest there are.
Turn the dial through the twelve intervals and follow the meter from smooth to rough — listen before you read the name.
On the staff: the interval you see before you hear it
On the page an interval shows up as the vertical distance between two noteheads, and there is a shortcut to reading it without counting: if the number is odd — third, fifth, seventh — both notes sit on lines or both sit in spaces. If it is even — second, fourth, sixth, octave — one is on a line and the other in a space.
That gives you the number at a glance; the quality, it does not. A third you see on the staff may be major or minor depending on the accidentals and the key signature — a semitone of difference does not move the noteheads. Which is why reading intervals is eye and ear together: the staff tells you the number, and the sound confirms the size.
Change the interval and watch the two noteheads: line-line, space-space or line-space.
Explore: any interval, from any note
Now all of it at once: choose the starting note, the interval, the direction — up or down — and whether the two notes sound in sequence or together. The starting note lights up in indigo, the arrival note in violet, and the full name appears. They are the same colours the game uses to reveal the answer.
Notice what happens when you change the starting note but not the interval: a perfect fifth still sounds like a perfect fifth from any key. That is what an interval is — a relationship, not a place — and it is what makes a melody recognisable in any key. Going down doubles the challenge: the same interval falling sounds different from the same interval rising, and the ear has to learn both.
Choose the root, the interval, the direction and the mode, play, and then change only the root to hear that the interval stays the same.
So, what now?
Intervals are not learned by memorising the semitone table: they are learned by hearing two notes, naming the interval and finding out straight away whether that was the one — many times over, in short sittings. That is what the intervals game does, level by level: it starts with major and minor thirds, adds the perfect intervals, the sixths, the octave, the tritone and the sevenths, and ends with both notes sounding together.
And if you want the complete table — every interval, with inversions, compound intervals and enharmonic spellings — a good music theory book has it in two pages, and this page is no substitute for that. It exists so that when you open the book, every line of the table already has a sound in your head.
Frequently asked questions
What is a third?
A third is the interval between two notes whose letter names, counted from the first to the last, come to three: C-D-E, for instance, or F-G-A. It comes in two sizes: the major third is four semitones (C to E) and the minor third is three (C to E♭, or D to F). It is the interval that gives major and minor chords their colour.
How many intervals are there?
Within one octave there are thirteen, counting from zero to twelve semitones: unison, minor and major second, minor and major third, perfect fourth, tritone, perfect fifth, minor and major sixth, minor and major seventh, and perfect octave. Beyond the octave they repeat with bigger numbers (ninth, tenth…) and are called compound intervals. The app's free practice offers all twelve from the minor second to the octave.
What is a perfect interval?
Perfect is the quality of the fourth, the fifth, the octave and the unison: intervals that do not come in major and minor, only in one size — five, seven and twelve semitones. If one of them grows or shrinks by a semitone it becomes augmented or diminished; between the fourth and the fifth sits the tritone. In Portuguese and Spanish the same intervals are called "justos", which is why you may see 5J where English writes P5.
What is the difference between a melodic and a harmonic interval?
It is the same distance sounding in two ways. In a melodic interval the two notes come one after the other, as in a melody; in a harmonic interval they sound at the same time, as inside a chord. The name and the semitone count do not change — what changes is what the ear does: following a leap, or perceiving the colour of a blend.
What is the tritone?
It is the interval of six semitones, exactly half an octave — F to B, for example. It can be written as an augmented fourth or a diminished fifth, which is why it earned a single name, tritone ("three whole tones"). It is one of the roughest, tensest intervals, and music uses that tension on purpose, to call for a resolution.
How do you train your ear to recognise intervals?
By hearing two notes, naming the interval and checking straight away, many times over — starting with a few intervals that are clearly different from each other, such as the major third and the perfect fifth, and adding one at a time. Singing the second note before you play it helps fix the size in your body. Short daily sessions pay more than one long session a week.