Big Lyre
The big lyre can be found northeast of The God of the Forge fast travel point.
To play the big lyre, you’ll need to first find the 3 small lyres scattered around The Forgelands. They will give you the order of the strings to play on the big lyre. At the big lyre, shoot the strings with arrows in the correct order to receive Coins of Charon.
Small Lyres
This lyre can be found in the south central part of The Forgelands.
To remove the barrier, you’ll need to pull the lever then use Apollo’s Arrow to shoot all 3 unlit braziers. Once the braziers have been lit, you’ll be able to play the lyre. The order of the strings is 1323.
This lyre can be found on the southside of the island east of The Forgelands.
To unlock the barrier, head northwest along the path to find an object between 2 statues. Carry the object back to the barrier and place it on the pedestal. Head inside to play the lyre. The order of the strings is 321.
This lyre can be found north of The Aqueducts fast travel point.
To access it, you’ll need to get both of the giant metal cubes down into the slit with the 2 lasers. If you have the Heavy Lifting ability, you can simply toss them in there. Once both are on the platforms, activate the pedestal to play the lyre. The order of the strings is 1413.