In diatonic set theory a specific interval is the clockwise distance between pitch classes on the chromatic circle (interval class), in other words the number of half steps between notes. Although this sounds simple and clear, it is very common amongst theory students to do mistakes when writing intervals. Why? Because different intervals may have the same number of half steps.

An example is the augmented fourth interval and the diminished fifth. Both have the same number of half steps (six) and therefore sound the same,  but still they are different, as the first is a fourth interval while the later is a fifth. So is there a method to help you avoid mistakes? Yes there is, and it consists of three simple steps: (a) Write on the staff the generic interval, (b) Count the number of half steps (frets on the same string on the mandolin), (c) Compare with the staff and add accidentals.

## Writing Intervals if you are a Mandolin student/player

As every fretted instrument, one fret of the mandolin corresponds to a half step. Therefore, the easiest way to play specific intervals on the mandolin is to play both notes at the same string-pair, and consult the below table for the number of frets (half steps) the two notes should be apart. Here it is: