When writing intervals on the staff, it is common to confuse intervals with the same number of half steps.
When writing intervals on the staff, it is common to confuse intervals with the same number of semitones.
For example, one may accidentally write C to F# (an augmented fourth) instead of C to Gb (a diminished fifth).
Although both intervals sound the same and look identical on the keyboard, one is a fourth and the other is a fifth.
Fortunately, an easy three-step process exists to reduce the risk of this mistake.
Let's write a minor third from C.
First, write the generic interval on the staff. For this example, we will write a generic third.
Next, figure out the number of half steps on the keyboard. Since a major third is 4 half steps, our minor third will be 3 half steps.
Next, figure out the number of semitones on the keyboard. Since a major third is 4 semitones, our minor third will be 3 semitones.
Finally, compare the staff and keyboard results. Add any needed accidentals to the staff.
For our next example, let's try a major sixth from F#.
First, write the generic sixth on the staff.
Next, figure out the half steps on the keyboard. A major sixth is 9 half steps.
Next, figure out the semitones on the keyboard. A major sixth is 9 semitones.
Finally, add any needed accidentals.
F# – D# is a major sixth.
For our final example, we will write a diminished fifth from B.
First, write the generic fifth on the staff.
Next, figure out the half steps on the keyboard. Since a perfect fifth is 7 half steps, our diminished fifth has 6.
Next, figure out the semitones on the keyboard. Since a perfect fifth is 7 semitones, our diminished fifth has 6.
Finally, add any needed accidentals. In this example, no accidental is needed.
B – F is a diminished fifth.
Use this chart to reference the interval-writing process.