When looking inside the loot table on the template behavior pack in the recent 1.18.0.22 beta, it added otherside music disc, which is the newest music disc made by Lena Raine. However, it doesn't generate inside dungeons chest. This can be checked and verified inside the template behavior pack in the latest beta. For comparison, the stronghold_corridor.json loot table has record_otherside in the loot table, but not inside simple_dungeons.json loot table.