British soul singer Joss Stone first performed with Melissa Etheridge in 2005, when the pair were brought together at the Grammys to pay tribute to Janis Joplin by singing “Piece of My Heart” onstage.

Joss Stone has never been wanting for power in her pipes. But the British-born vocalist enjoys quieting things down as well on her intimate “Less Is More” shows — like the one she’s bringing to Sound ...