Instrumental Duet Double Bass,Instrumental Duet - Level 3 - Digital Download SKU: A0.851877 By Katy Perry. By Bonnie McKee, Dr. Luke, Henry Walter, Katy Perry, Lukasz Gottwald, and Max Martin. Arranged by Caroline McCaskey. Pop. Score and parts. 8 pages. AltStrings #2072159. Published by AltStrings (A0.851877). This engaging, gig-ready arrangement of Roar is easy to read and fun to play! Duet for Two Basses.