I wanted to remix something that I had
carefully archived a few years ago. Unfortunately, it's in NanoStudio 1 format and having upgraded iOS past the last version that supported NanoStudio 1, I can't reopen the project, nor is there an easy path to upgrade the project to NanoStudio 2's format. But it's not a total loss. I've at least got the midi parts out, so I can reconstruct it with different instruments.
So, there's a lesson here about not always doing OS upgrades without thinking about it. And I tend to archive my work done in NanoStudio 2 in it's own format, but maybe I should be rendering individual tracks to wav files, as space-consuming as that is.