"Costak" soundtrack uses the sounds of the area Petri lived and includes a song played by a Greek lyra. A closely related instrument of of the Black Sea kemence. Here is a nice folk belief relating to music provess and a Cretan hilted dagger.
"Whoever wants to become a good lyra - player should go to an isolated crossroads at midnight. First he should trace a circle on the ground with a black - hilted dagger, then enter it, stay there and start playing the lyra. A little later the Fairies will come and start hanging around him. Their purpose is not good, they want to do him harm, but since they cannot enter the circle, which has been traced with a black - hilted dagger, they try to lure him out in every possible way. They use blarney, they sing him nice songs, they wheedle him in a thousand and one different ways, but if he is wise, he must remain calm and continue to play the lyra without leaving the circle. If they fail, they invite him out of the circle in order to teach him how to play the lyra better. He must refuse. Then they will ask him to give them the lyra. The lyra - player should give it, cautious to let his arm or other part of his body out of the circle, because it will be amputated or he will go insane.
Then a Fairy starts playing the lyra with great virtuosity and afterwards they return the lyra to him, hoping that he will be persuaded to leave the circle and they will be able to harm him". According to the description of Nikos Politis, the continuous interchange of the instrument between the Fairies and the lyra - player, without anyone of them passing the limits of the circle traced with the black - hilted dagger, continues all night long until the first cock crows. Then they ask him to give them something of his own and they promise to teach him how to play the lyra like them in return. The lyra - player usually gives them one of his nails and they in turn teach him how to play the lyra with great virtuosity and then disappear at daybreak.
For this reason, in earlier times, if a lyra player played his instrument with outstanding virtuosity, he used to say: "What do you think? I learnt to play the lyra at the crossroads".
Source: The Cretan Dagger