The octave is the most consonant interval. It doubles the frequency, and it is the foundation of the Western musical system: two notes an octave apart share the same name and are heard as the same note in different registers.
1. Visual shortcut: spotting a octave on the staff
Octaves are a matter of recognizing spatial patterns on the staff.
The mirror rule: an octave always changes the kind of position, like fourths and sixths.
- If the lower note is on a line, the upper note is in a space.
- If the lower note is in a space, the upper note is on a line.
An octave covers exactly 4 lines and 4 spaces, with six free positions between the notes. It is a wide, balanced distance. Example in treble clef: C4 (first ledger line below) and C5 (third space).
2. Reference table
The octave is usually perfect, but in advanced theory its variants are also considered:
| Interval quality | Half steps | Harmonic classification |
|---|---|---|
| Diminished 8th (d8) | 11 | Conditional dissonance (enharmonic to a major 7th) |
| Perfect octave (P8) | 12 | Perfect consonance |
| Augmented 8th (A8) | 13 | Conditional dissonance (enharmonic to a minor 9th) |
3. Identify octaves
These exercises identify perfect octaves and their variants. The note name stays the same while the register changes a lot.
4. Build octaves
A root note appears on the staff. Choose the type of octave and click the position of the second note.
5. Printable octave worksheets (PDF)
The same two skills, on paper: one sheet to identify written octaves and another to write them. Each has 42 melodic octave intervals in treble clef spread over seven staves, starting with natural, ascending notes —the perfect octaves that come out of the natural scale— and ending with sharps and flats and mixed directions. No exercise repeats the same two notes.
Identify octaves
Under each interval there is a line to write what kind of octave it is and whether it ascends or descends (P8 ↑, d8 ↓…).
Download the worksheet (PDF A4) Answers
Write octaves
The reverse exercise: the first note and the interval to form are given, and the student places the second note on the staff, with its accidental if it needs one.
Download the worksheet (PDF A4) Answers
You may print and photocopy them freely for the classroom. Each answer sheet is the same worksheet with the answers in red, so you correct by laying one over the other. The rest —including the sheets that mix several intervals— is in interval worksheets in PDF, and if you want new sheets every time or to practice on screen choosing the intervals, in the custom interval quiz.
To train your ear as well, use the reference tones of the online tuner and compare the sound of each interval with a pure tone. The online metronome helps you build sight-reading speed.