Mysterious Song
Getting to Nemar Cave

Outside Nemar, go around the south-eastern bend to reach the cave (7) to the north-west.
Nemar Cave
First, you will have to make your way to the deeper levels of the cave. You will start near the north-west and will need to make your way to the exit at the north-east, taking the route via the south.
If you wish, you can take some detours along the way to collect Herbs (depicted by the leaf icon) and Ether (the mortar-and-pestle icon), but if you get attacked enough times, you might end up consuming them immediately anyway.
Before you go down, there is a suit of Magic Mail (armor icon) north of the exit.
Retrieving the Tools
You need to circle from the east to the west, south, east and north. If Ark has not given you his quest, a Dark Knight (X) will block your way. He will not fight you, but not let you go further either.
If you have got the quest, the Dark Knight will be standing to the east of Vyper (1) instead. You will have to fight Vyper for Ark's tools.
Depending on your level, this can be quite a difficult encounter. If Ryanna knows X-Fire, have her cast it on Vyper.
There are some Herbs and Ether scattered around the map, as well as Revive (smiley face). The central chest to the north of Vyper holds a Dark Sword (sword icon).
Backtrack all the way to Nemar Cave F1 and then to Nemar and speak to Ark. Although he remains standing in place, the bridge you need repaired will have been fixed when you leave town.