Marissa would be singing Crazy by Gnarls Barkley. CLEARLY. (video|lyrics)
Just because it sums up their courtship so well, someone would have to enable Sev and Amalie by singing Been A Long Day from How to Succeed In Business Without Really Trying with them. (video)
Felicity would of course be singing Adelaide's Lament from Guys and Dolls, because the only thing that's causing more stress than the tearoom is wanting Fabian to stop being so damn noble. (video)