When your playing you want all of the valves to react the same. I just picked up my Bach and played a little, When I push number one valve there is a little different resistance then number two. The sound changes a little also. When you play the trumpet all the time you get used to it. I picked up my Monette and played the same stuff and each note feels the same and I get the same sound. When you use combinations of valves I guess something has to give up but it feels all the same to me. I am not a trumpet expert. I'm sure there is someone on here that can explain it better. This is the general idea though.