He doesn't think much of the blushing, just happy with the compliment? And also she did just sing and dance around a bunch. while playing an instrument. Actually, that's kind of amazing she can juggle all of that. Prompto knows he'd just try and faceplant if he even attempted doing two of those things at once, let alone all three.

"Right, there's a difference between the two. What is it exactly? Do bards specialize in something?"

Well... he's not entirely wrong...