·         Example [17.1] is a quartal form of G13.  We can re-order the notes so that the hard dissonance (F-E) is on the inside and the soft dissonance (B-A) on the outside of the chord (Example [17.2]).  Sometimes these are referred to as the A and B forms of the chord respectively - though I don't like this terminology because A and B are also note names, which could lead to confusion.

·         The form with the soft dissonance on the outside is a very handy inversion which can be slotted into a progression of quartal thirteenths as a tritone substitution to give a satisfying sense of harmonic motion.  For instance, Example [17.3] presents a sequence from A13 to G13 via an intermediate inverted Eb13 (tritone substitution for A13) and so on through Db13 to F13 to B13...

·         Δ7 chords, like quartal thirteenths, also include hard dissonances that can be clustered by inversion.  Example [17.4] is DΔ7 with the minor second on the inside of the chord.

·         Clustered forms of 13 and of Δ7 can be neatly interconnected.  In Example [17.5], Eb13 (the tritone substitution of A13) resolves onto DΔ7 with the smallest of upward chromatic shifts.

·         The minor second cluster is such a distinctive feature of these chords that they can be slimmed down into three-note structures.  Example [17.6] is Eb13/DΔ7 voiced in this minimal form.

·         The cluster format of DΔ7 will also serve as a voicing of B-7(9).  The resolution of clustered F#13 onto B-7 9 is presented in Example [17.7].

·         If it's difficult for the ear to make sense of these rather exotic chord voicings and resolutions, play them against bass root notes in the left hand (Example [17.8]).

·         Clustered 13 shapes in the left hand can be very usefully combined with open right-hand triads (second inversions seem to work especially well).  Running the triads through part of a diminished scale adds a rich, free dimension to the basic dominant.  Example [17.9] does this for Eb13.