The notes in the natural harmonic series that can be played range from the 1st to the 12th natural. Since the 1st natural speaks, pedals can also be produced.
Unlike the tenor trombone, only six positions (slide lengths) are playable when the contrabass trombone is tuned to F1 (valves closed). Each position lowers the pitch of the natural harmonic series by a half tone. Good players can overblow to the 12th natural.
With the Eb valve
In the Eb1 tuning (open Eb valve) five positions are playable:
With the Bb valve
In the Bb0 tuning (open Bb valve) five positions are possible:
In the Ab0 tuning (both valves open) four positions are possible:
In the shortest (1st) position the tube length of the F tuning is 386 cm. In the Bb tuning the tube length is 724 cm in the longest possible (5th) position. So when playing the lowest note on the contrabass trombone the musician has to vibrate an air column which is nearly 3.5 m long! Trombones also exist which do not have a Bb valve (fifth-valve) but a C valve (fourth-valve).
The naturals no. 2 go down as far as Gb1 and have more substance than the corresponding pedal notes on the bass trombone.
As a rule the pedal notes are used as well. The pitch of the notes below B0 is no longer clearly identifiable.