ON SEPTEMBER 3RD, 1970, Joni Mitchell stopped by the BBC’s Television Centre in London to perform for the premiere of their In Concert series. She would play songs from previous albums, including “Cactus Tree” from her 1968 David Crosby–produced debut and “Chelsea Morning” from Clouds, but the majority of her 11-song set came from her then-new album, Ladies of the Canyon. With tracks like “Big Yellow Taxi” and “The Circle Game” — the latter her response to Neil Young’s “Sugar Mountain” — Ladies of the Canyon marked Mitchell’s first platinum record. It was also her first to feature the piano, an instrument she’d use to produce warm, introspective songs less than a year later on Blue.