You emerge in a massive cavern divided in two by a bottemless chasm. The only way across is a rope bridge with old but sturdy wood planks. It was this swaying structure that was causing the moaning. However, the haunting melody came from the other side of the cave. You proceed to cross the bridge without incident and without looking down. Once back on solid ground the melody changes to a soft tune as it detects your presance. A glow from an alcove reveals the origin of the music. It's the Crystal Dragon!