Joan Baez is as bravely eclectic as ever. The world’s best-known female folk singer is 73, and back in London for a remarkable four-night stint at the Festival Hall, where she mixed 60s nostalgia with contemporary, Latin, political and gospel songs, along with reminders of her traditional roots. She came on stage solo, sporting a bright red scarf, clutching her guitar as if she were back at a folk club. She started with the traditional Handsome Molly, presumably because it begins with the line “I wish I was in London”, then changed direction with the reflective Steve Earle song God Is God and Bob Dylan’s Farewell, Angelina. Her voice was not as strong as it once was, but still distinctive for its purity and phrasing. This was an intimate, thoughtful performance in which she constantly changed musical direction.

After the third song she introduced her “band”, which consisted of her son, Gabriel Harris, on percussion, concentrating on the cajón box drum, and the remarkable multi-instrumentalist Dirk Powell, who started out on banjo before moving on to guitar, piano, fiddle and squeezebox. He even pulled out a cuatro when Baez began discussing her musical campaigns against South American dictators, and provided thoughtful backing for the Nicaraguan song Mi Venganza Personal. Noting that her “trademark is songs of misery”, she followed with a bleak song of death and revenge, La Llorona.

Coming back to English-language ballads, she included a quietly powerful solo treatment of The Great Silkie of Sule Skerry, “which I haven’t sung for 30 years”, but which was one of the best songs of the night. By the end Baez was switching between a Virginia mountain workout and the stirring Union song Joe Hill, and less welcome revivals of Catch the Wind and Imagine, before she returned to South America with Gracias a la Vida. She deserved the standing ovation.

• Until 21 September (except Friday). Box office: 0844-875 0073. Venue: Royal Festival Hall, London.