Alan Sharkis post_id=51214 time=1507562972 user_id=1714 said:
So, lets say that for the sake of notation PAs and CBAs are concert-pitched, as opposed to transposing instruments like trumpets (mostly Bb, although C trumpets also exist) and saxes (Bb or Eb except for the rare C-melody sax).
This can get more confusing if you look more closely, though. In most of the world, outside of the UK, music for the tuba, trombone and euphonium is in concert pitch, but their natural tonal key if you will is Bb (though the tuba may also be found in C, Eb and F.) So a euphonium for example might be playing the same part as the Bb cornet (but an octave lower), and operating the valves just the same, but one of them is in Bb and the other is in C, by this notation standard.
Brass instruments have a clear natural key, corresponding to the length of the main branch of the tubing (not including valve tubing), but as they are nowadays all equipped with valves, they can play with equal facility in different keys. A woodwinds natural key doesnt depend on its acoustics in that way, but rather on the conventional way its holes and mechanism are matched to the 10 fingers of the right and left hands. The key determined in this way, comes from the lowest note on the early woodwinds, such as recorders - a recorder whose lowest note is C, has similar fingering to a C flute. (The notation came later, though - music for early woodwinds was all concert pitch, as far as I know.) Flute and saxophone are simple examples; the clarinet, though, departs acoustically from the norm and sounds different notes for the same fingering, in the upper and lower registers, so though normally classified as a Bb instrument, it plays like an Eb alto saxophone in its lower register. The bassoon is mechanically an F instrument, but like the trombones and tuba, its music is written in concert pitch.
In short, even these distinctions are as much arbitrary as natural.