This month’s Fleetwood Mac Fest sounded like a dream — Carly Rae Jepsen, Courtney Love, and Joanna Newsom all performed! — but it would’ve been even dreamier with the added angelic voice of Florence Welch. Thankfully, Florence + the Machine sensed that they were missed, and while performing at last Friday’s War Child benefit concert at St John at Hackney Church, they debuted their cover of Fleetwood Mac’s breakup ballad “Silver Springs.” (They’ve previously done “The Chain.”) And like a woman hell-bent on taking her rightful place as Stevie Nicks’s other moon sister, Florence Welch knocked it out of the park. Calling on the power of the braided crown, she emphasized the raw emotion of the song, giving a more bare-bones take on the original. Because, like Stevie, Florence will follow you down till the sound of her voice haunts you.