If 11-12 follows Ryuk's suggestion and heads for the ballroom, he may hear the voice before he reaches it: a rich but light soprano voice singing
a sensuous aria, full of longing:
Mon cœur s'ouvre à ta voix,
comme s'ouvrent les fleurs
Aux baiser de l'aurore!
Mais, ô mon bienaimé,
pour mieux sécher mes pleurs,
Que ta voix parle encore!*
Once he enters, he will find a woman with long, wavy dark hair, standing by a window, a music stand before her, singing with arms outstretched, then slowly drawing her hands in toward her heart, as if beckoning any listeners or some unseen lover to approach.
Mag has been working on expanding her repertoire and that includes relearning arias she'd set aside, as well as learning new material. But she's starting to tire just a little from a day of practicing and she'd welcome the chance for a break.
*"My heart opens to your voice
Like the flowers open
to the kisses of the dawn!
But, oh my beloved,
to better dry my tears,
Let your voice speak again!" -- Unfortunately, that is not Sarah Brightman singing it in the vid I've linked.