Afterdark draws its inspiration from the steam engines in the Power Hall of the Museum of Science and Industry but describes what the engines do once the exhibition is closed. In a steam engine, the water boils and the resulting steam travels to the motor unit where the expansion and contraction of the pistons create movement. In Afterdark, this action-reaction is simulated at the beginning where specific musical events trigger others in different instruments. The steam traveling in the machine is portrayed by the sound crossing the stage from right to left. ​
The first section is very mechanic and repetitive as it is supposed to be a ‘literal’ translation of the steam engine. In order to create a wide range of metallic sounds, the percussionists will be using saucepans, pan lids, a break drum, a car spring as well as other more conventional instruments. The following section uses the same metallic sounds to create rhythmic patterns found in Latin-American dances. As the piece progresses these sounds are mixed and then replaced by skin (e.g. bongoes, tom-toms) and wood (e.g. guiro, woodblocks, slapstick) sounds. Afterdark ends with a return to metallic sounds and an accelerating ‘machine noise.’