i am hosting a plugin-only minecraft server and i have increased the world height through a datapack generated by worldpainter.
i connect with some client-sided mods, including this one, and songs that are set to play deep underground or underground do not play at any Y-level. but in a different server or singleplayer world without any height changes, it works fine. it flat out doesn't work on a server if it has any world with height changes, because i tested on other worlds in the same server that did not have any height changing datapacks attached to them.
the server is running velocity with paper version 1.21.4, and my client is running fabric 1.21, in case that matters at all.