Marty looks over just in time to see Ankh messing with his iPad, and he gets the idea. He grins and looks over their group, bobbing and weaving with the music. This moment is calling for something else; not completely obnoxious to ruin the music, but enough to add the right touch. So he looks over to Rarity!

He raises his eyebrows, not wanting to yell over the music and distract everyone, if that's even possible. He grins, as if to say you should sing!