The next interval to consider is the **perfect fourth**. The perfect fourth the equvalent of 5 semitones (the same as between the first and fourth notes of the major scale). It comes in a handy single-string form ...

... as well as a two-string form:

The Perfect Fourth is the **complement** of the perfect fifth. This means that adding a these two intervals together results in a octave (7 + 5 = 12). “So what?”, I hear you cry. Well, we don't always play arpeggios in their most basic form. Often we will use a combination of notes from triads within separate octaves. The Perfect Fourth helps us navigate between the triads because it is the interval between the 5 in one triad and the 1 in the triad an octave higher.

For example, If we combine our two D Major arpeggios from the previous section, there is a Perfect Fourth between the two notes on the second string (A - D):

Using our new-found knowledge, we can add one more note to the shape. We know that for every root (1) there is a ‘5’ a Perfect Fourth lower. A perfect fourth below our lowest D is A (string-4/fret-2):

The final interval we'll consider is the **Minor Third**. It is equivalent to 3 semitones and, like the other intervals we've considered appears on the mandolin in two forms. We've already encountered this interval between 3 and 5 in the major arpeggio but, for the sake of completeness, here are examples of both forms:

Single-string form:

Two-string form:

We can now express our D Major arpeggio as a note-clock:

Now would be a good time to review everything we've covered so far and try to reinforce your grasp of all the concepts introduced. Make sure you have a good understanding of our full D Major arpeggio shape - maybe play through all the notes saying “one”, “three” or “five” as appropriate, until the notes begin to feel and sound familiar and the note-relationships within the shape begin to make sense.