If the music is written for the C trumpet it is.... like reading a chuch hymnal (where the songs are written in C). On a Bb you would have to transpose as you read. If you had a C-Trumpet you would just read the music with your normal Bb fingerings. The only catch is that your eye and your head will be fingering an "A" (lets say with 1st & 2nd valves) but your ears will hear a note that you normally call a "B". This takes some getting used to, and is worse with other pitched horns (D, Eb, F, G, A-Picc). You also need to spend a bunch of time on page 125 with a slow metronome and a tuner to re-learn where all your pitch centers belong. They are not always the same as on your Bb (like sharp A's and flat D's, etc....). On my C trumpet the 2-3 valve low Ab (sounds like a Bb on a Bb horn) is WAY flat and I have to really listen to lip it where it needs to be in a way that I don't have to do on my Bb horn. I played a musical last week... I was on the 2nd book. I got there first and the guy playing 1st showed up and played the whole book (written for Bb) on his C trumpet (and on an Assymetric mpc). Initially was was "WTF!!??"... but, the guy was pretty much nails. The book had lots of goofy key changes and often went from key of B to Ab, or F#. Lots of runs with accidentals too. He blew right through it. The book had a bunch of D's and maybe one or two licks higher than that up to one with an F#. He was great. He has just trained himself to think in C rather than our Bb centric training.