Has rainbow-colored confetti ever fallen over Benaroya Hall before Sigur Rós played there last night? During “Gobbledigook”, the clap-along, sing-along, extra-drummers called from the wings closer of their main set, the foggy indoor air was met with technicolor spotlights and filled with paper showers. And then they came back for an encore.

If the symphony hasn’t already added special effects to the repertoire, they just might have cause for considering it.