Music Intervals Explained - Names, Semitones, Inversions

An interval is the distance between two notes. Every melody is a chain of intervals, and every chord is a stack of them. If you understand intervals, scales and chords become easy to build, and you can start to hear why music sounds the way it does.

Two notes played one after the other form a melodic interval; played together, a harmonic interval.

The two parts of an interval name

Every interval name has two parts: a number and a quality. For example, "major third" or "perfect fifth".

Step 1: the number (count letters)

Count the letter names from the lower note to the upper note, including both. Ignore sharps and flats at this stage.

• C to E: C, D, E = 3rd
• C to G: C, D, E, F, G = 5th
• D to C: D, E, F, G, A, B, C = 7th
• Same note to same note = unison (1st); C to the next C = octave (8th)

On the staff this is easy to see: line to the next line is a 3rd, line to the next space is a 2nd, and so on.

Step 2: the quality (count semitones)

The quality tells you the exact size. Intervals fall into two families:

• Perfect intervals: unison, 4th, 5th, octave.
• Major / minor intervals: 2nd, 3rd, 6th, 7th. Minor is one semitone smaller than major.

Either family can also be augmented (one semitone larger than perfect or major) or diminished (one semitone smaller than perfect or minor).

Interval chart with semitone counts

This is the table to know by heart. Examples are measured up from C.

Why spelling matters

C to F# and C to Gb sound identical (6 semitones), but they are different intervals: C–F# is an augmented 4th (C, D, E, F = four letters) and C–Gb is a diminished 5th (C, D, E, F, G = five letters). In the same way, C–G# is an augmented 5th while C–Ab is a minor 6th, both 8 semitones. The letter count tells you which name is correct, and the correct name tells you how the note functions in a chord or scale.

Inverting intervals

To invert an interval, move the lower note up an octave (or the upper note down). C–E becomes E–C.

Two rules make inversions instant:

• The numbers add up to 9: a 3rd becomes a 6th, a 2nd becomes a 7th, a 4th becomes a 5th.
• The quality flips: major ↔ minor, augmented ↔ diminished, perfect stays perfect.

Examples: C up to E is a major 3rd, so E up to C is a minor 6th. G up to C is a perfect 4th, because C up to G is a perfect 5th.

Inversions are a practical shortcut: a major 7th is hard to count, but "a semitone below the octave" is easy.

Compound intervals

Intervals larger than an octave are compound intervals. Subtract 7 from the number to find the simple interval: a 9th is a 2nd plus an octave, a 10th is a 3rd plus an octave. Chord names use them: the "9" in C9 is D, a major 9th above C.

Consonance and dissonance

Some intervals sound stable and blended (consonant), others tense and wanting to move (dissonant). This is about stability, not about "good" and "bad": music needs both.

The tritone inside a dominant 7th chord (in G7, the notes B and F) is the main source of tension that pulls back to the tonic chord.

Recognizing intervals by ear

The most reliable method that does not depend on memorizing tunes is the scale method: sing a major scale from the lower note and notice which degree the upper note matches.

• M2 = do–re, the first step of a major scale
• M3 = do–mi, the bright sound of a major chord's lower two notes
• P4 = do–fa, strong and open, often heard as a "call" upward
• P5 = do–sol, hollow and powerful, the power-chord sound
• M6 = do–la, wide and warm
• M7 = do–ti, one step short of the octave, very tense
• P8 = do–do, the same note higher

Then learn the minor versions as "one semitone narrower": m3 sounds darker than M3, m2 sounds like a tense half step, m7 sounds like the top of a dominant 7th chord.

Major scale from C: compare each note with the first

Practise in short daily sessions with the ear trainer. Start with only two intervals (for example P5 and M3), and add a new one when you score above 90%.

Intervals on the piano

Count every key, black and white, from the lower note to the upper note: each step is one semitone. Then name the interval by letter count. Example: from D, count up four keys (D#, E, F, F#) to F#. Four semitones and three letters (D, E, F) = major 3rd.

Intervals on the guitar

On one string, each fret is one semitone, so the interval equals the number of frets.

Across adjacent strings in standard tuning (except between the G and B strings), the shapes are always the same. Measured from a note on the lower string to a note on the next higher string:

Between the G and B strings, everything shifts one fret higher (because that pair is tuned a major 3rd apart, not a 4th). The octave is two strings up and two frets higher, or three frets higher when the G–B pair is crossed.

On the bass

The four bass strings (E A D G) are all a perfect 4th apart, so the table above works on every pair of strings with no exception. Bass players use a handful of shapes constantly: the perfect 5th is one string up and two frets higher, the octave two strings up and two frets higher, and the perfect 4th below is the same fret on the next lower string.

These shapes are the building blocks of root-fifth lines and arpeggios: see arpeggios on the bass.

Practice

1. Name these intervals by number and quality: C–A, E–G, F–B, D–Bb, A–E, B–F.
2. Build the interval above each note: M3 above Eb, P5 above B, m7 above D, M6 above F, TT above C.
3. Invert each interval from exercise 1 and name the result.
4. On guitar or piano, find a perfect 5th, major 3rd and minor 3rd from five different starting notes.
5. Spend five minutes a day with the ear trainer, starting with P5 vs M3.

Next steps:

• Worksheets: Intervals 1, Intervals 2 and Intervals 3.
• Print the intervals chart.
• Explore individual intervals: perfect 5th, major 3rd, tritone.
• Lessons: The major scale, Triads and Ear training.
• Follow the ear training path for a structured routine.