By now, the world is familiar with the artistry of England’s Florence Welch, the powerful vocalist-frontwoman of the popular indie-rock band that bears her name. She’s partial to laying down her massive, layered gospel voices over soaring orchestral synths and booming percussive flourishes. Less familiar is the more subdued side of the London-born singer. On her band’s fourth album, Welch strips her music back to its bare essentials. “Grace,” a touching tribute to her younger sister, is just piano and vocals. “No Choir,” as the title suggests, also eschews anything but voice and keyboards. There are tracks with lusher instrumentation, including “Hunger,” a confessional about her teenage eating disorder, and the thunderous “100 Years.” But Welch, who has also released her first book, Useless Magic, a collection of her poetry, lyrics and artwork, is clearly intent on showing a difference side of herself: highly vulnerable and more intimate. The less-is-more approach suits the talented siren.