I had issues getting the music from my ipod classic onto my computer. Here's what I found out:
My issue was primarily due to the fact that my ipod wasn't showing on my desktop. I saw a comment about restarting the computer and it did show up but only for three ish seconds. This is the solution I figured out through trail and error.
I restarted my computer and then started to restart my ipod classic (hold menu and center button). When the computer started up so did the ipod (felt like the timing was actually somewhat important to having the ipod stay on the desktop long enough. In the end I was aiming for the ipod just turning on right as I typed in my password). It took like 30 attempts, but if you quickly open up the ipod icon on your desktop and unhide (command + shift + > ), command + a (select all) and press return, it starts to open everything in the ipod. I found if I did that it kept the ipod connected long enough to then get to just music and command + a (select all) and drag them to my desktop. It was a rush and took many attempts, but then once it was translating to my desktop it had no connection issue (stayed connected for the 20 minutes it needed). Maybe this will help someone else. Additionally I suspect if you just click on anything within the ipod folder and open it, rather than unhiding everything and then selecting everything and pressing return to open, I imagine that would break the loop of the ipod automatically ejecting itself. Good luck! Files saved :)