transposition info incorrect when switching between score and part
I have marked this critical since it may cause loss of data, and it renders the linked parts feature essentially useless with transposing instruments.
Steps to reproduce using Windows 7 (c92b058):
1) open attached score
2) with Concert Pitch on, verify you see all C's in both staves, key signature of F major
2) with Concert Pitch off, verify the alto staff shows high A's and a key signature of D major
3) with Concert Pitch still off, view linked alto part
Expected result: alto part should show a high A and a key signature of D major
Actual result: alto part shows a high A but a key signature of F major (and reports concert pitch is now *on*)
At this point, part is now incorrect but there is no data loss - you can return to the score and see all is at it should be. You can toggle Concert Pitch mode on and off and the alto staff on the score always displays correctly. And if you turn Concert Pitch *on* while viewing the score, then view the alto part, it correctly shows the alto part at concert pitch: C's, key of F. Turn concert pitch *off* while viewing the alto part, and it appears correct: high A's, key of D.
However, if you then return to the score at this point, you again see the high A's, key of F; Concert Pitch now reports that it is on. Hitting Play confirms that the score is now incorrect. Toggle concert pitch off at this point and the display shows high F#'s, key of D.
It appears the transposition info is now permanently mangled, but it is possibly to reverse the procedure and mangle it back to shape. With the score show concert pitch *on* (high A's, key of F), return to the alto part. It will now show the correct results for concert pitch *off* (high A's, key of D), and will report that concert pitch is indeed off. Toggle concert pitch on, and the alto part correctly displays the C's and key of F. Return to score and everything is back to normal.
It appears that MuseScore is trying to remember the state of the the Concert Pitch toggle for the score and parts independently, but then not applying that information correctly.