I am reading through a miniature score book of the Vorspiel (Prelude) of Die Meistersinger Von Nürnberg by Richard Wagner. It's a piece for orchestra, including two B-flat clarinets.
The clarinet part is written with confusing key signature changes.
The orchestra begins with the key signatures of 0 sharps (ignoring the horns and trumpets), and as expected the B-flat clarinets are in the written key signature of 2 sharps. This is normal. This continues for 96 bars, until the section ends (with double bar lines).
At measure 97 there is a key change with the orchestra moving to 4 sharps. However, the clarinets (Kl.) change to 0 sharps, which is not what one might expect (6 sharps).
At measure 109 the next section beings with the orchestra now in 3 sharps, but the clarinets moves to 4 sharps! This is very strange as I would expect 5 sharps for there to be agreement — but lo and behold nearly every A (what would be the 5th sharp) is sharped with an accidental.
This section ends, and bar 118 seeing a return to 0 sharps for the orchestra, and 2 sharps for the clarinets which is normal again. There are two more key changes but the clarinets continue with 2 more sharps than the rest of the orchestra like normal.
I've summarised this information in a table below: (where '+' indicates sharps, '-' indicates flats)
|Orchestra in C||0||+4||+3||0||-3||0|
|Clarinets in Bb||+2||0||+4||+2||-1||+2|
The two section that are odd are bars 97-108 and 109-117.
I think 97-108 can be explained by the fact that a key signature of 6 sharps is probably challenging for clarinet, and perhaps it is more practical for the players to have no key signature here, instead having accidentals on basically every note instead.
But I don't have a good explanation for is 109-117, why is the clarinet part written in 4 sharps, and not 5 (or 0)?
I note that there would be enough time for a change (muta) to clarinets in A here, but this isn't indicated, and the transposition would then need to change (which it doesn't).
I can imagine that this whole piece would actually be easier for clarinets in A (except perhaps 122-150).
I've looked up some other versions of the piece on IMSLP, and found two other versions of the score, as well as the clarinet part in isolation, but they all seem to have the same strangeness in the clarinets parts key signatures changes for measures 97-108 and 109-117.
My questions are:
Does my interpretation of bars 97-108 seem reasonable?
What is going on with bars 109-117?
Would the clarinet players actually find this to be the best way to read/play the music?
Is this kind of thing normal for clarinets (or other transposing instruments)?
Is there some other explanation?