A bright laugh comes at Byleth's accusation. "I must plead ignorance on any guilt as to my attempts to spoil you." He is. It's quite obvious that he is.

And, well, they have space here. No time and place such as the present to play for one he desires to court so much. He preemptively positions himself so that Byleth will be able to see both his profile and him playing upon the keys. It's simple work to pull the piano out with his enchantments, bench and all, and he settles himself upon it with practiced ease. He's played plenty already tonight, so no need for a warmup.

Instead he simply begins to play. The first piece is passionate, but without the thundering power he can achieve, a lighter thing, showing his affection for the one be plays for. When the energetic end comes, he holds his fingers over the keys and waits for Byleth's verdict, smile at a rare ease that comes with sharing his soul, eyes soft.