I have a jazz band chart that I composed in Finale in the key of Bb. I brought the midi file into Reaper and everything was working fine for several days. Then today, I opened the file to do some work and discovered the entire chart. all 16 tracks wer now playing in the key of F. Any ideas as to what could I could have done to shift the entire chart down 5 semitones or more importantly how to get it back to the original key? I've looked at ReaPitch, but it looks like I would have to install 16 versions of it, one for each instrument to shift the instruments back to where they belong. I'd rather figure out how this go screwed up to begin with. Any insights are greatly appreciated.

There are Transpose options in the MIDI editor, and I think you can also do it by right-clicking a MIDI item in the normal view and going into its Properties. Not sure how that would happen by accident though.

Fixed 

Thanks for the help. Don't know what happened, but got it fixed by adjusting the item properties for each track. Just one of digital life's great mysteries.