I’ve struck gold. Well actually my friend and colleague Wayne Garcia struck gold and passed it along to me.

It’s a full concert by Stevie Wonder — easily downloadable online — from Jan. 31, 1974 at the Rainbow Theatre in London, recorded after Inner Visions came out, but before Fulfillingness’ First Finale. Allegedly, the show was taped for official release, but scrapped, which gives this bootleg remarkably good sound quality.

It’s easy to hear why the tapes were filed away. Stevie’s set is sloppy, random and unfocused — and that much more interesting for it.

The 23-year-old, in the early stages of a hot streak that made him probably the most important artist of the ’70s, is backed by the three-piece rhythm section of guitarist Michael Sembello, bassist Reggie McBride and drummer Ollie Brown, along with a couple of woman background singers.

Eric Snider is the dean of Bay area music critics. He started in the early 1980s as one of the founding members of Music magazine, a free bi-monthly. He was the pop music critic for the then-St. Petersburg...