Rei's own smile turned up, a wide, happy and excited expression that genuinely touched her eyes. Rarity's voice came out as lovely as always, and she had to follow up. Stepping forward, she spins as she sings, lowering her violin and just reveling in the music.

He had to fight back tears of rage.
His heart beat like a drum.
For with the wife of his best friend,
he spent his final night of freedom.

That stanza hits her hard, something in the words jogging out an uncomfortable feeling too, and she spins away, getting out of the center and trying not let her distress show. Ivan might catch it, though, or someone else that knows her. Not...a good feeling, not a pleasant memory, but not enough to pull her out of the musical reverie.