As Strange wasn't there at the concert, he's only got other people's stories to tell him what happened. Those stories are a mish-mash of different details that all add up to something downright confusing. Shadow creatures, mesmerizing music, and Nightshade for some reason.

Why was she there in the first place...it's something that Strange still doesn't know.

"What did the music sound like to you?" Strange leans against the wall of his trailer as he asks that, hands going back into his pockets. "I've got a feeling the enthralled will think the music sounds completely different than what it actually was."