The problem is, Bob, if I play an "A" on my trumpet (reading from my music that would be the 2nd space up in the staff), you will hear a "G". For you to hear A = 440, I will have to play a B. That's the note I use to tune with for orchestra or playing with C instruments. For band, I play a third space "C", but the C instruments have to play Bb to play the same note.

Sorry, but the tubing does make a difference for brass instruments because that's the way they are made. Yes, they do make trumpets in the key of C, but Bb's are more popular. As Mac sez, they do sound different. If you play a "C" instrument, such as piano, etc., you don't have to be concerned unless you are trying to arrange for what some are referring to as non-concert instruments. I call them non-C instruments because that's what they are. C instruments determine what the concert key is. If the key signature for the C instruments is D (2 sharps), the key signature for the Bb instruments is E (4 sharps). Yes the pitch, for a given note, is absolute---for the C instruments. The OP is just learning the tenor sax (Bb) so he has to be in the correct key to play in tune with the non Bb instruments.

Stan

Cornet Curmudgeon