A question about the terrible sound this game calls music

[Halivel]

How can you even play as a quartet in this game? Latency won't allow you to sync with other player's music as far as I'm aware.

There's actually an option exactly for syncing since 5.1: Patch Notes. Sometimes it's a good idea to pay more attention to what developers add into the game.

Quote:

Ensemble mode has been added.
This feature helps ensure all party members will be heard in sync by players in the vicinity.

Accessing Ensemble Mode
From the ready check menu, select Enter Ensemble Mode then commence the ready check.

Setting playback type to Self Only will mute the performance of party members.

Setting playback type to All Members will play the instruments of all party members with an increased delay.