Dave) brass instruments are on Bb pitch, strings are on C and so on becuase these instruments sound best at these keys.

That is not entirely true. trumpets come in different keys. Some are at Eb, C, and even G. And Frenchorns are pitched in the key of F. And to sum up the issue with the highest a trumpet has ever gone. as someone else has said it is all about the players limits. The way their umsure is set makes the difference. And just for a fun fact. If a trumpet player who has not been playing long tryed to hit a super C the pressure that builds from trying to play such a high note could cause the person to have an aneurism. Thought that would be interesting to let people know.