Caplin further explains that there are two main types of pre-dominant harmonies, "those built above the fourth degree of the scale () in the bass voice and those derived from the dominant of the dominant (V/V)" (p. 10). The first type includes IV, II6 or II6, but also other positions of these, such as IV6 or II. The second type groups harmonies which feature the raised-fourth scale degree () functioning as the leading tone of the dominant: VII7/V, V6V, or the three varieties of augmented sixth chords.