I found some more info on LJ, this is very cool!

https://aefallen.livejournal.com/5412.html - All the links are broken, but 2003!
https://buffy-icons.livejournal.com/371209.html - Same for this
https://yummy-songsets.livejournal.com/2898.html - And again, hmph.
But yummy-songsets has a quick primer on songsets in their profile! https://yummy-songsets.livejournal.com/profile

Some more LJ songset comms:
https://titan-songset.livejournal.com/profile
https://naruto-songset.livejournal.com/profile

A few more posts:
https://zombieful.livejournal.com/929.html - 2004
https://crapnahalficons.livejournal.com/10848.html - 2004
https://icon-heap.livejournal.com/1508.html - 2005

And interesting- one from 2015! https://summer-of-giles.livejournal.com/398974.html