

The number is the signal you send to the program. There’s a lot of signals you can send (not just 15 and 9).
The difference between them is that 15 (called SIGTERM) tells the program to terminate by itself (so it can store its cached data, create a save without losing data or corrupting, drop all its open connections gracefully, etc). 9 (called SYGKILL) will forcefully kill a program, without waiting for it to properly close.
You normally should send signal 15 to a program, to tell it to stop. If the program is frozen and it’s not responding or stopping, you then send signal 9 and forcefully kill it. No signal is “better” than the other, they just have different usecases.










And that’s why I think it’s an issue. The least popular tracks, which are the most likely ones to disappear from the internet, are the ones they store in the lowest quality. While I’m glad they made this huge effort for preservation, and understand the limitations of storage space, I also wish they would have at least preserved the original 160kbps streams.