I wanted to know about the difference in the keys of trumpets(or infact any instrment). Example,if I were to take a Bb trumpet and play a note on it and produce a Concert Bb note on it,withou any valves pressed down on course. What happens if I use a C trumpet and play without any valves pressed down also ,does it still produce a Concert Bb? Or does it produce a Concert C? Or any other note? I am still confused.I only know of songs or parts of songs or movements being in a key,but I do not know the difference between instruments of different keys,other than the length and sound.