Instrumental Duet Instrumental Duet,Marimba,Vibraphone - Level 3 - Digital Download SKU: A0.1031487 Composed by Jackson Cates. Contemporary. Score and parts. 2 pages. Jackson Cates #3434375. Published by Jackson Cates (A0.1031487). Inner Mechanics Outro was originally for a short film called Inner Mechanics. Unfortunately due to some logistical problems, the film was never released. This is a duet for vibraphone and marimba (4.5 octave), which features a fun 4:3 polyrhythm. Find a friend and just have fun!