Need help with Clarinet part

If you ask a clarinetist to play an A you will get a concert-pitch G because the clarinet is a transposing instrument pitched in Bb.

If you want the clarinetist to play a note that sounds the same as an A played by the non-transposing instruments in the orchestra (a "concert-pitch" A) then you when you are writing the part for the Bb clarinet you would write a B (they start off two semi-tomes down and need to play two semi-tones higher to sound the same).

MuseScore helps you avoid the need to transpose on the fly by providing you with a "Concert Pitch" option button. Create a score with all your instruments set up for time signature, tempo etc. but leave out the key signature for now. Press the Concert Pitch button and then place the same key signature for each instrument. Enter all the notes as you want them to sound i.e. enter an A if you want it to sound A, B if you want it to sound B etc. and ignore the fact that some of the instruments (Bb clarinet etc.) are transposing. Play the notes on a piano or other non-transposing instrument if it helps you.

When you have finished entering all the notes, turn Concert Pitch back off and the notes and key signatures will automatically get transposed for the transposing instruments.

Note that there are some instruments that play in C and you might think that they are "concert pitch" but they are actually transposing instruments as they play an octave or two down from what might be written for them. When you enter notes in Concert pitch for them you might need to change the clef to G8 (octave down) or whatever but leave this for a piece that is more advanced than what you a trying to do for the current exercise.

Yes, if you want the clarinets to play the pitch you would identify as "A", then enter it as "A" with "Concert Pitch" enabled. Then when you go to print the parts, turn Concert Pitch off, and it automatically turns into an B (not A#; clarinets sound a whole step lower than written, not a half step).

As for why clarinets (as well as many other instruments) do this, it's actually to make things *less* confusing to the players. And to explain why, I'll relate to your experience as a string player.

As you are presumably aware, the upper three strings of a viola are the same as the bottom three strings of a violin. And your four strings are exactly an octave higher than the four strings of a cello. So to some extent, if you know how to play one stringed instrument, you have some possibility of playing them all. You won't be very good, of course, because the fingerboard lengths are so different that you'll struggle with intonation big time. But at least in principle, you understand that if you want to play a "B", you can do this by placing your finger at a certain position on the G or A strings, and that works on all three instruments.

This works because the strings of all these instruments are tuned essentially the same way. And that means that violin players, viola players, and cellists all will usually prefer to play in keys that allow them to use the open strings, or at least, not have to play very far up the finger board a lot. So you tend to like the key of C and dislike the key of Db.

But did it ever occur to you that if you tuned each of your strings a half step higher, then you could play in C but have it come out in Db? Wouldn't that be nice? Then whenever someone wanted you to play in Db, they could simply write in C, tell you to tune everything a half step higher, and you'd be in business - it would be easier to play and sound better than if you tried to play in Db. And if someone handed you an instrument tuned that way - Db-Ab-Eb-Bb - wouldn't you still want to read music for it as if it was tuned C-G-D-A rather than have to learn a whole new set of fingerings?

Well, that's more or less what the inventors of wind instruments did. Except rather than have people tune their instruments higher or lower, they simply made bigger or smaller variations of each instrument. So they can all play in C but have it come out sounding like other keys by choosing which variation of the instrument they play. Over the years, the other variations of the clarinet became less common and Bb became most common - which is to say, when they play what for them is C, it comes out Bb. It's as if you tuned all your strings a whole step lower. The Bb clarinet is most common, but other variations are found in professional orchestras (A and Eb especially).

You might wonder why people settled on the Bb clarinet rather than a C clarinet as the one that would become most common, and I can't answer that. But at least the basic reasons why some instruments sound differently than they are written might make more sense to you now. It's so people can play instruments that are tuned differently (to facility playing in different keys or just to have different ranges available) without having to learn a whole new set of fingerings.

I know right?? The clarinet pisses me off every time... I usually just put the note randomly, then toggle it with the arrows up and down till my ear tells me its on the right spot.