Not tuba or euph - but conical
This is not tuba or euphonium, but they are conical instruments. Hope it's ok to post this here David.
There are two excellent videos of a recording session with some Vienna horns. There are 12 players and what a sound!! The Vienna horns use the double-cylinder (or pumpenvalve) from around 1840 - which supposedly offers less resistance to the player. Still has that 'natural horn' sound. The videos have some pretty good close-ups where you can see the valve action. One of the players has a couple of cable ties holding his crook together (at least I think that's what that first loop is called). I was surprised to see some of their embouchures using so much top lip. A hornist I discussed this with told me they might have been playing some of the very low notes.
Vienna Horns videos