Incompatible with "Create Mechanical Extruder".
Crash on launching.

latest.log

Yes, in both cases an earlier error disrupted loading. I made a fix which hopefully should prevent melodies from showing up in the tracelog.

If you want to find the true cause of errors, watch for "Cowardly refusing". This should never appear and indicates that something is already completely broken at that point, everything after that is irrelevant.

This issue and #26 seem to be the same thing. This seems to be linked to this commit which is meant to cause a crash when a custom item is invalid, but appears to be crashing when creating the bagpipe item.

Strangely I only started crashing like this when updating certain mods - and then when I update other mods it seems fine. Can't make heads or tails of this issue, hope a swift resolution is possible!

So... this error message is a red herring; it's masking the actual cause of your crash:

net.minecraftforge.fml.ModLoadingException: Mod §ecreate_mechanical_extruder§r only supports §3kubejs_create§r §o1902.2.4-build.20 or above§r §7Currently, §3kubejs_create§r§7 is §o1902.2.4-build.18
Which is basically saying kubejs_create is out of date.

Still very strange that Immersive Melodies is making itself show in such crashes, something that should certainly be addressed here.

EDIT: If you're having trouble finding the real crash message, it's in latest.log, not crash-reports.