This piece is scored for tenor Wagner Tuba in B♭ (optionally for horn) and piano.
It can be played on a single Wagner Tuba in B♭, but ideally on a compensated or even double one as the written cadenza asks for notes that aren’t available on a single wagner tuba.
The same way, the cadenza requires multiphonics that might not be possible to be sung on the player’s vocal range. So, the cadenza can be simplified, changed and the players can even write their own cadenzas, in order to fit their instrument, vocal range, and playing abilities.
Because it was scored having an instrument in B♭ in mind, some technical passages might become tricky if played on the F side.
There are written improvisations for both instruments between letter D and G, that also present chord symbols, that can be transformed into real live improvisations.
Ricardo Matosinhos