Frisk's presence shifts from the set of chimes to a ukulele (which shudders) to a trumpet (that soundlessly slides) to settle on a massive drum (that thrums). It's the closes thing to that wall.

They know someone is here, but the person isn't clear like all the things are. A blur in the air, one they can't focus on without a spike of pain like a headache through their whole being.

The drum rocks in place in their discontent. They don't realize this.