Which Music Discs Trigger Dancing in the Jammies Mod
Any Disc Works
In the Jammies Mod, the dancing behavior is tied to the jukebox playing music, not to a specific disc. That means any music disc you insert into a jukebox will cause nearby zombies and skeletons to start dancing. You do not need to hunt down a rare disc for the effect to work.
Practical Disc Choices
Since every disc triggers the same dancing behavior, pick discs based on how long you want the dance to last and what you have available. Longer tracks keep mobs dancing for a longer stretch, which is handy if you are building a display or recording a clip. Short discs are fine for a quick test to confirm the mod is working. Discs obtained from vanilla sources like dungeon chests, creeper drops, or fishing all function identically here.
Testing the Effect
If you are unsure whether the mod is active, insert any disc into a jukebox with a zombie or skeleton standing nearby. If the mob starts dancing, the mod is working. If nothing happens, check that the mob is actually within the short radius of the jukebox and that the disc is genuinely playing. Note that the mod only affects zombies and skeletons, so other hostile mobs will ignore the music entirely.