I recently acquired a bass that used to be a high school instrument. It's seen some heavy use. Worn and chipped corners and the like. I also found a paper airplane inside of it. The bridge wasn't put on it, but I knew enough to get it in its proper place and to get tension on it properly. The issue is that when I tune all the strings to the proper pitch, I go back to the first string and it's already down half an octave from where I tuned it to. I'm completely befuddled, and my lack of knowledge is most likely to blame. I come from the guitar side of these forums.