This one's a real head scratcher. I'm working on a Windows 10 computer, in Acid PRO 10.😶
I created a MIDI track in a separate program, and imported it into Acid. I assigned an instrument library to the track (the Choir libraries). That's the set up; the library doesn't seem to matter, as what happens below happens across 3 different libraries.
If I listen to the track in the Clip Properties window, which is where I'm normally working in MIDI, everything sounds fine. If I play the track from the main Acid window, the entire thing plays 3 semitones down, in the wrong key! Example; C2 becomes A1. I made exports from three different Vita libraries with the exact same issue, and rendering to audio track produces the same result.
My theories are a) since this is happening with libraries, Acid is somehow assigning the MIDI notes to the incorrect note files of the library, in a systematic and consistent way, or b) Acid is transposing the MIDI itself before playing the note files for the export.
I really enjoy using these libraries, so a solution to this issue would be greatly appreciated.