The fourth is a basic distance in harmony. It is the interval between the tonic and the subdominant of a key, and it appears everywhere in classical music, jazz and folk music.
1. Visual shortcut: spotting a fourth on the staff
The crossing rule: a fourth always changes the kind of position.
- 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.
Between the two notes there are two free positions (a line and a space, or a space and a line). Example in treble clef: E4 (first line) and A4 (second space), with F4 and G4 skipped.
2. Reference table
The perfect 4th is one of the most stable and powerful intervals in music. Here are the three types:
| Interval quality | Half steps | Harmonic classification |
|---|---|---|
| Diminished 4th (d4) | 4 | Conditional dissonance (enharmonic to a major 3rd) |
| Perfect 4th (P4) | 5 | Perfect consonance |
| Augmented 4th (A4) | 6 | Semi-consonance (tritone) |
3. Identify fourths
These exercises train quick recognition of perfect fourths and tell them apart from augmented fourths (the tritone).
4. Build fourths
A root note appears on the staff. Choose the type of fourth and click the position of the second note.
5. Printable fourth worksheets (PDF)
The same two skills, on paper: one sheet to identify written fourths and another to write them. Each has 42 melodic fourth intervals in treble clef spread over seven staves, starting with natural, ascending notes —the perfect fourths (and the augmented fourth F–B) that come out of the natural scale— and ending with sharps and flats and mixed directions. No exercise repeats the same two notes.
Identify fourths
Under each interval there is a line to write what kind of fourth it is and whether it ascends or descends (P4 ↑, d4 ↓…).
Download the worksheet (PDF A4) Answers
Write fourths
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.