The crotchet triplet is a rhythm common in all genres of music. It is well suited to jazz since jazz rhythms are based in triplets. A crotchet triplet is the twice the length of an eighth note triplet, and there are three crotchet triplets in the time of two quarter notes.
These exercises begin with crotchet triplet and inverted crotchet triplet comping patterns. The lesson continues with a range of different comping rhythms based in crotchet triplets. Even though the comping rhythms are not explicitly notated as crotchet triplets they are still crotchet triplet rhythms.