Either the screen will go black and the music will continue, or the screen will become a garbled mess with the last note of the music continuing to play.
I made sure the IPS files weren't in the same directory as the patched rom.
These crashes are easily repeatable. I'll savestate at the beginning of a battle just in case it crashes, because it seems there are also some enemy abilities that are able to crash the game. If I just repeat some specific actions I can reliably get it to crash. The most reliable way seems to be to use the blue magic spell Snowstorm on certain enemies.
Just in case it was an issue with Lunar IPS, I put the non-patched rom in a separate directory with the IPS so the emulator could automatically patch it. Swapped the SRAM file over, loaded the in-game save, and still had the issue. I suppose I could start fresh in case there's something wrong with the SRAM, but it would take a very long time to get to the point where I can try to replicate the issue.