Bloodstained: Ritual of the Night

After beating the third boss, Craftwork, you'll be able to move a pillar and get a free ride from a demon in a chariot. Immediately after this you'll start seeing small four armed fairy monsters called Carabosse, repeatedly kill them until they drop their shard for you (4% drop chance.). In the same area right after the fairy monsters start appearing there is a gazebo with a piano in it, sit in the chair in front of the piano with the Carabosse familiar out and it will sing while you play the piano. Let the entire song play and the achievement will pop.

Area: Garden of Silence
Familiar: Carabosse

After moving the pillar and traveling via the Coach you can find Carabosse here to farm for the shard and then a piano to sit at with it equipped. Remain seated for the entirety of the song to unlock the achievement.

Make sure the Faerie is your Familiar when you play the piano, and you'll get this achievement after listening to the whole song.

As soon as you get the "Craftwork" ability from the Craftwork boss, go back to the Coachman in the central area and move the rock blocking the way, talk to him and board his chariot, he will take you across the gap, in the next room you'll find a fairy type demon named "Carabosse", kill it until it drops the Carabosse familiar shard, keep going right and you'll find a piano, press and enjoy the beautiful song, the Achievement will pop right after Miriam leaves her seat.

Short video guide with full song here : https://gamerdvr.com/gamer/orb1t4l/video/76233446