For some reason, whenever I try to picture Grand Hallway’s in-studio performance on KEXP this afternoon, I keep conjuring images of a circus clown cars. And that’s no comment on Grand Hallway’s lovely, pitch-perfect songs; I’m just curious how all these people will fit into one room, let alone a studio. The orchestral pop band performs today at 3 p.m., with backing from a Seattle Rock Orchestra octet. If every member of Grand Hallway shows up, that’s 16 people in one studio. I’m predicting a sonic earful from that performance.