"Liminal" is, first and foremost, an homage to John Mackey's love of progressive metal bands such as Tool. A rhythmic tour de force, focused on the percussion section (including a part for six tom-toms), the work is concerned primarily with groove and pulse, with moments of as many as three time signatures happening simultaneously.

Liminality is the quality of ambiguity or disorientation that occurs in the middle stage of rituals, when participants no longer hold their pre-ritual status but have not yet begun the transition to the status they will hold when the ritual is complete. During a ritual's liminal stage, participants "stand at the threshold" between their previous way of structuring their identity, time, or community, and a new way, which the ritual establishes.

(John Mackey)