Obsidian is a duet for low brass and percussion written for Kayla Aftahi and William Akers and premiered in April of 2021. The low brass part can be played on trombone, euphonium, or tuba (and there is also an additional version for Horn in F). This piece features many ethereal sections with the two instruments exchanging motives and switching roles. These sections are punctuated with more rhythmic and often aggressive sections. The piece also features some multi-percussion sections with the percussionist playing marimba, bass drum, and cymbal as well as the brass player even playing the brake drum.

The percussion part requires a 5.0 octave marimba.

For more information about Lucas, including his other published works, visit his composer page.