How this instrument works
A musical interval is the distance between two pitches, and within a single octave every possible distance has a standard name tied to its semitone count: 0 semitones is a Unison, 1 is a Minor 2nd, 2 is a Major 2nd, and so on up through 12, which is a full Octave. Each name combines a size (2nd, 3rd, 4th, and so on, counting letter names) with a quality (minor, major, perfect, or the special case of the tritone at exactly 6 semitones), and within one octave the semitone count alone pins down exactly which name applies.
This instrument works purely from semitone count, which means it doesn't distinguish between enharmonically identical spellings that music theory sometimes treats as conceptually different — 6 semitones, for instance, could in principle be called either an augmented 4th or a diminished 5th depending on the musical context, but both are the identical distance in semitones, and this instrument simply calls it a Tritone.
Interval names like this are the building blocks of chord construction — a major triad, for example, is defined as a root plus a Major 3rd (4 semitones) plus a Perfect 5th (7 semitones) above it — so this instrument pairs naturally with this site's chord calculator, which uses exactly these named intervals to build triads from any root note.
- Enter Number of semitones — any whole number from 0 to 12.
- Read Interval name directly beneath the input.
- 0 semitones returns Unison and 12 semitones returns Octave — the two boundary cases of a single octave span.
- Values outside 0–12 are rejected; this instrument covers one octave's worth of intervals only.
Worked example — 7 semitones
Enter Number of semitones = 7. Looking that up in the interval table gives Interval name = Perfect 5th, matching 7 semitones exactly.
7 semitones is the distance from, for example, C up to G, and the Perfect 5th is the second-most-consonant interval in Western music after the octave itself — the interval the entire circle of fifths, and much of tonal harmony's chord-building, is organised around.
Questions
What's the difference between a 'major' and a 'perfect' interval?
Perfect labels the unison, 4th, 5th, and octave — intervals that were historically treated as maximally consonant and stable, and which don't come in major/minor pairs. Major and minor instead label the 2nd, 3rd, 6th, and 7th, where a minor version is always exactly one semitone smaller than its major counterpart at the same letter-name distance.
Why is 6 semitones called a 'Tritone' instead of augmented 4th or diminished 5th?
Because this instrument works purely from semitone count, and 6 semitones is the exact midpoint of the octave — equally far, by that count alone, from being read as an augmented 4th or a diminished 5th. Both names refer to the same distance; 'Tritone' is the semitone-based name that sidesteps having to pick one spelling over the other.
What if my interval spans more than an octave, like 13 or 19 semitones?
This instrument covers 0 to 12 semitones only, a single octave's range. Intervals larger than an octave are called compound intervals and are typically described by subtracting 12 (or a multiple of 12) to find the equivalent interval within one octave, then noting it's 'plus an octave' or more.
How does this connect to the chord calculator on this site?
Chords are built by stacking named intervals above a root note — a major triad is a root plus a Major 3rd plus a Perfect 5th, for instance. This instrument lets you look up exactly what any given semitone distance is called, which is the same vocabulary the chord calculator uses to describe how it builds each triad quality.
Is 0 semitones really considered a musical interval?
Yes — a Unison, two notes at the exact same pitch, is the smallest possible interval by definition, even though no distance separates the notes. It's the natural starting point of the interval scale, just as 12 semitones (the Octave) is its natural endpoint within a single octave span.