Multiphonic overtone issue

[Onebaplayer]

So here is a very specific problem I am having.

I am trying to learn Fnugg off of Oystein Baadsvik's "Tuba Carnival" album. He plays Eb tuba, I play a Gronitz piston F. My issue is that I can not sing Bb on top of the bass clef staff. I am a singer as well as a tuba player, and my pitch is on. Ive checked it away from the horn, and with the overtones of the actual notes on the tuba, sans voice. The issue is something about the characteristic of the horn is keeping me from singing that specific note. When i try to slur through the range of the instrument (with voice) I find partials that feel almost like when I slur from my chest voice into falsetto. My Bb on the horn is in tune, and regardless of the fingering i cant sing the note through the horn, in tune. I've already done my best to feel around the horn for any spots that are resonating more on that pitch, but to no avail. Any suggestions on how to fix this would be greatly appreciated.

Lastly, I did try playing it up a step so that the fingerings would be the same as Oystein has on his Eb. I encountered the same issue, so I'm wondering if maybe its a partial that just doesnt want to be sung on my horn.

[Art Hovey]

I've encountered that same annoying problem. I don't think it's the fault of the instrument. My conjecture is that the vocal cords are way back in the throat, adding several inches to the distance which sound waves must travel. In effect, my vocal tract acts like extra tubing, lowering the pitch of vocal resonance in the tuba. I find that forming my mouth to make an "EE" sound instead of "OO" reduces the severity of the intonation problem, although the resulting tone is not what I want. I hope to hear comments about this from tubists who have managed to overcome the problem.

[Onebaplayer]

Yeah that has also helped me a bit. Interesting idea, sounds totally right to me. Unfortunately the piece REQUIRES making that "EE" syllable, but at other times needs to be open for contrast. Seems that maybe singing above the pitch should correct that. Unfortunately, that is not something I've felt as possible yet. It just skips up to a whole step higher when i try to compensate.

[windshieldbug]

Since you're implying that its situational, I'd recommend trying it with another horn entirely or (humor me) a different mouthpiece to see if the resonating frequencies are the same. A third resonance variable is you!

[Gravid]

I had similar difficulties while trying to learn Fnuug on a B&S (Symphonie model) F. However, I was having trouble getting the pitch on the played notes down to where it needed to be, to match the hummed notes. Subsequently, I ended up using usually-very-flat alternate fingerings. After spending a lot of time trying to re-learn the fingerings for Db and Eb, I finally just punted and tried the piece on several other horns:

• Mirafone 184 CC (slightly better pitch, but still considerably #)
  Mirafone 1292 CC (still better pitch, but more difficult to balance the humming against the playing)
  B&S 606 CC (same as above, but balance still more difficult)
  King 2341 BBb (BINGO -- easy to tune the intervals, and easy to balance the humming/singing)

Couldn't help but notice that the larger the bore size of the horn, the easier it became to perform the multiphonics w/good intonation; however, it also became more difficult to balance the humming/playing. I also wonder if the key of the instrument (and subsequent overtone series) has anything to do w/the intonation of the multiphonics?