Big Lyre
The big lyre can be found directly south of the Goddess of Wisdom fast travel point.
To play the big lyre, you’ll need to first find the 2 small lyres scattered around the Grove of Kleos. 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 is located south of The Archives fast travel point near the border with Valley of Eternal Spring.
To unlock the gate at the entrance, you’ll need to solve several puzzles. First, directly in front of the entrance on the lower level you’ll come across a pedestal and an unlit brazier with corruption. R2 the brazier to remove the corruption then light it using the Apollo’s Arrow. Once it’s been lit, activate the pedestal next to it. To the east of the entrance, you’ll see 3 large cubes behind barriers. Walk up the small path to the right of the stairs and push that cube back onto the platform. Next, push the cube closest to the stairs north onto the platform. Head to the cube in the middle and push it back against the platform along the back wall. Return to the northern cube and push it down the stairs to the platform below then activate the pedestal. For the western puzzle, stand on the circular platform and look left to find a small room with a breakable wall. Break the wall using your axe then grab the metal cubes. Return to the circular platform and throw the cubes into the newly opened holes. Once both platforms inside have been lit, activate the pedestal on the left. With all 3 pedestals activated, head inside and play the lyre. The order of the strings is 2134.
This lyre can be found in the far northeastern corner of the Grove of Kleos.
To unseal the entrance to the building, stand on the circular platform and look towards the giant statue. Use Apollo’s Arrow to light both of the unlit braziers. This will open the barrier between the stairs. Head inside and smash the breakable wall behind the platform. Push one of the giant cubes in the back room onto the platform to unseal the entrance to the building across the way. Head inside and play the lyre. The order of the strings is 143.