Question about the physics of the instrument.
We all are familiar with the "false partial" that exists between the 2nd partial and open fundamental of an instrument- in this case an F tuba has a Bb resonate between the open Fs (shown in the first measure). Then, beneath the open fundamental of the instrument, we can use normal fingerings to descend further. Using a 6 valve system, you can go chromatically down from the fundamental F to all-valves-down "pedal F", F0 in scientific pitch (shown in measure 2).
What I'm wondering about is the Bb between those 2 Fs in question, Bb0, as a secondary, "sub-fundamental", open false partial. On my F tuba, I can get that note to speak, open fingering, with similar resonance to the Bb an octave higher between F1 and F2 (the established and well known false partial). Is this the same principal that applies? Then one could theoretically descend all the way down to the Bb-1 as shown (essentially 6 valve fingerings in the key of Bb). I can only get down to Eb0 using this method, but that is still lower than it "should be possible". Someone with better ultra-low range facility may be able to go even further down than that (still on F tuba), theoretically speaking.
Maybe it's not a real note/partial at all and the horn isn't actually resonating at all, despite feeling like it is?
