Instrumental Duet Instrumental Duet,Trombone,Tuba - Level 3 - Digital Download SKU: A0.799472 Composed by Drake Mabry. 20th Century,Contemporary. Score and parts. 9 pages. Drake Mabry #3010563. Published by Drake Mabry (A0.799472). Stochastic Duo for trombone & tuba was written during 1986 when I was working at the Xenakis UPIC studio in Paris (Clamart), France.  The use of probabilities in the form of a duo enabled me to incorporate the stochastic character while still having a dialogue between two instruments. There is also a piano piece 'Stillness' based on this same principle. The duration is 7'45.