Instrumental Duet Instrumental Duet,Trombone,Tuba - Level 3 - Digital Download SKU: A0.1015691 Composed by Michael Mettler. Arranged by Michael Mettler. Instructional,Standards. Score and parts. 6 pages. Michael Mettler #4837159. Published by Michael Mettler (A0.1015691). This Trombone/Tuba duet takes you through an evolution of church music from Gregorian Chant to a more Contemporary Style. It could be used to increase awareness of both technique and historical context. .