Joy of Cooking’s tangy blend of folk and blues never quite blended with the mainstream. Back to Your Heart, a collection of previously unreleased tracks, gives a taste of what made this combo so special. The band was led by two women — singer/keyboardist Toni Brown and singer/guitarist Terry Garthwaite — which set them apart from their post-psychedelic peers. But Joy of Cooking deserved praise for its supple, percussion-driven rhythms and ability to interweave old-time tunes with original material. Garthwaite’s purring yet gritty vocals (suggestive of a mellower Janis Joplin) and Brown’s simmering electric piano lent a warm ‘n’ funky glow to the proceedings. Highlights among the studio recordings here include the gospel-rooted “Summer Fire” and the wistful “Song for Silent Wings.” Live renditions of “Castles” and a freewheeling medley of “Brownsville” and “Mockingbird” capture the Joy’s on-stage chemistry. The jazz-dipped “Song In Blue,” a recent collaboration by Toni and Terry, finds the group’s core members whipping up their old magic. These archival recordings show that Joy of Cooking’s recipe is worth rediscovering.