Incorrect pitch being played

I just created a new score, and added a handful of instruments. I went to start writing in the notes, and while everything looks fine, every note placed plays back as being an entire 13 (one octave and a fifth, for example, A4 on the staff makes the sound for E5) above where it is on the staff. I don't know what could be causing this -- I literally just created the score, and didn't touch any settings before attempting to write on the staff. I am pretty new to Musescore, so I might just be missing something, but I have no clue what it could be. The clefs are all correct, and I didn't add any 8va markings. All pitched instruments (Violin, Cello, Electric Bass, and Grand Piano) are doing this, and the unpitched Drum Set instrument is only allowing notes to be placed in one position on the staff. Does anybody have any idea what is going on here?