files > Blazhevich etudes as duets > Study #1 > Original key of C Major > Contrabass octave
BlazhevichTuba70-#1 Duet String Basses.pdf
2nd must have an extension to low C - still: in the 2nd part, bar #37, the last note differs from most other versions due to range limitations.
BlazhevichTuba70-#1 Duet Contrabass Tubas EASY.pdf
2 contrabass tubas in bass clef concert - not really an easy version, but it is directed towards instruments with too few valves to play the low B natural found in the original 2nd part.