I know this is old but I would just like to mention that I have actually played F0 on a B Tuba personally using the standard buzzing technique so I can vouch for that note definitely being in the extended range of a Tuba In principle even a standard 3 valve Tuba should be able to play E0 a half step lower as long as the instrumentalist can buzz that low Which is very hard to do imo 76 14 232 104