As for building a cimbasso oneself, some members of this forum are more capable than others.
I like the approach of Sam "Tubanurse" Gnagey as displayed at
viewtopic.php?t=2904
A wonderful sample of:
Which parts are available?
How do I combine them into a workable instrument?
Utilising the bell, bottom bow, and the next one or two branches from whatever shape of American baritones will work for the bell section.
The luck or genius of Sam was the availability of a 4-piston 0.687" valve block (as I read it originally from a King Eb sousaphone).
But there we touch in at one of my sore points: scavenging from older instruments.
Personally I am not into King sousaphones, as I go for antique Conn’s on that matter. But that does not imply, that I find, that the King’s should be scavenged. They should be with players/collectors going for the King sound, which is most relevant, even if I happen to have a different preference.
One type of scavenging, which is fairly easy to come by, is acceptable, as everybody knows, that plastic sousaphones just about are made to die. If one follows the market, one will see bulks of them with chips and cracks beyond repair.
One model especially leaves off a very relevant valve section: the Conn 22K. Sadly it only has 3 valves.
Ranting a bit, but I am a collecting brass historian at heart. And at the same time I am a great admirer of inventive minds like Sam Gnagey and Joe Sellmansberger, even if their approaches and personal styles are very different.
Klaus Smedegaard Bjerre
PS: A high-end euphonium with a main tuning slide trigger could do most cimbasso parts in regards of range and dynamics. Even the best American 4 valve baritones would run into intonation problems in the sore range above the open pedal Bb. And both would emanate a wrong sound.
The cimbasso is a valved bass trombone, not a small bore tuba/euph. Verdi wrote some devilish difficult passages, but then modern bass trombone players have become unbelievably accomplished in technical matters. Even the lowest contrabass trombone passages from Wagner are easy on a modern bass trombone in Bb. The sound may be a bit on the lighter/brighter side, but still hugely preferable to anything coming out of a tuba or a euphonium/baritone.