Nico di Angelo.

*Will walks to the Hades cabin do his weekly checkup on Nico, but then he hears the soft strumming of a guitar and an amazing voice...he looks through the window and sees Nico sitting on his bunk bed, with a guitar on his lap. when Nico was little he, Bianca, and his mother, Maria would sing as she cooked for them. then Will noticed silent tears streaming down Nico's face as he sung a foreign melody.*