I'm not trying to argue here, but I thought long and hard about answerring because I am contesting what the previous poster and previous posters have said about the differences between Bb and C trumpets and the word BRIGHT.
Ok, here's the lowdown, FROM AN EXPERT on the subject.
C Trumpets:
frequently are constructed with a copper bell system
Have a narrower tubing and less flared swelling throughout
Have a smaller valve structure
Utilize a smaller mouthpiece with a sharper conical bore
Smaller mouthpiece creates faster wind cycles
Bb Trumpets
Are typically brass from start to finish
Use a larger cup for the mouthpiece
Larger cup creates larger slower wind cycles
Have larger valves/pistons
Have a shorter but quicker bell flare
Have a more extreme tubing flaring througout
Ok. There are many other physical and scientific differences between the two. I am not going to mention them all.
Now, regardless of their pitch, even if they were both Bb or C instruments, the fact of the matter is that, regardless of pitch, the harmonic and fundamentals structure of the C Trumpet, because of it's physical characteristics aside from pitch (length of overall trumpet), have more partials and overall frequencies present at greater proportional volumes in the higher frequency spectrum than the same note played on a Bb trumpet, even if they were the same transposing instrument. This has to do with the many physical differences I mentioned above.
This result of greater volume of upper partials, in all certain terminolgies translates to what is generally accepted by most of the world as BRIGHTER. Yes, the C Trumpets ARE brighter.
Now, taking into account the physical differences and the transposition differences, the C Trumpets have the following advantages over teh Bb trumpets:
They require less air per note
They can play with more agility
They can especially reach about a minor 3rd higher than the Bb trumpet because of all the physical differences combined, without any further emboucher or airflow changes from teh the same note on the Bb
They can start and end a note more quickly
They will pierce through the same orchestration better than a Bb trumpet regardless of pitch (read: also in the low registers)
Now, on the flip side of the C Trumpets which are BRIGHTER, are the Bb Trumpets which are referred to as WARMER because of their opposite mechanics from teh C Trumpets.
Without getting to labored here, let's just say that the Bb trumpets do not have those things that I mentioned above regarding the C Trumpets special abilities.
One thing worth great mention is how nearly non-existant any composing is in the low register of the trumpet. From E3 to C4. A professional with the right mouthpiece can use this range for slow to medium passages and the trumpet section itself can sound fantastic together in chords harmonized with the trombones in this low register. It really has yet to be done. But I hope to change that.
Evan Evans