eupher61 wrote:I'm not sure what you were meaning there, triplet.
It's not the fingerings. Yes, any valved British-style transposed treble clef part will read "middle c" as open fingers. The deal is getting the correct pitch alignment between an Eb part and a BBb part, since they both read their respective parts in transposed treble clef as "middle c - open valves," but the pitch is a major 4th different.
Here's the deal. In the USA, it's used mostly by Eb baritone sax players (and to a lesser extent, Eb contra clarinet players) in reverse when there is no bari sax part available: take any standard USA concert band bass clef concert pitch tuba part. Eb is one ledger line below the staff. Take any standard USA concert band bari sax part. Their written middle c, fingered all six fingers and the lower right pinky paddle, is one ledger line below the staff, but the actual pitch is that same concert pitch Eb, one ledger line below the bass clef, as in the concert pitch tuba part. So bari sax players take the tuba part, mentally change the clef to treble, add three sharps to the key signature, adjust the accidentals accordingly, and play on.
Inversely, to get from a British brass band Eb transposed treble clef notation tuba part back to concert band bass clef concert pitch notation, you do the opposite: mentally change from treble clef to bass clef, add three flats, and adjust accidentals accordingly, so that the notated middle c note, which sounds the same pitch as concert Eb one ledger line below the bass clef, is in the correct alignment on the staff, and it doesn't matter whether the tuba playing the bass clef concert pitch notation part is BBb, C, Eb or F, because American concert band tuba players are taught to read the pitch and adjust fingers accordingly to the instrument.