SAN FRANCISCO — Maybe it was all the sequined outfits, but for a split moment in time, Sigmund Stern Grove became a disco club.
By the time Diana Ross arrived in style at Stern Grove Festival, she was deep into her Celebrating Timeless Classics tour, having performed the previous night at The Mountain Winery in Saratoga. At 81, the Queen of Motown has kept remarkably busy, and her performance on Sunday at the festival-closing Big Picnic show proved she’s not ready to hang up the microphone.
Amid the green trees, the excitement was palpable. Organizers had received over 200,000 ticket requests for this free concert. San Francisco Mayor Daniel Leer rang the heritage bell per tradition…