Bill Graham was the rock concert promoter in the San Francisco area from the 1960s until his death in 1991, and his company, Bill Graham Presents carried on until it was acquired ultimately by Clear Channel. The company’s archives, including thousands of concert recordings, were acquired by Bill Sagan who digitized and catalogued them to open “Wolfgang’s Vault” (a reference to Graham’s family nickname). Wikipedia calls it “one of the largest collections of live concert recordings available to the public” and there are several legendary performances online, and certainly numerous legendary performers. You do have to sign in and provide an email address to listen, but it is free. The vault also contains reproductions of vintage t-shirts, posters, and photographs. It’s a rock memorabilia treasure trove.