A great one, indeed - a mentor for Dave Holland and Tony Williams whose work is some of the most satisfying jazz of the 70s. Improvisational, atonal, but always managed to sound like music. A real loss that should be commemorated not only with his own great albums, including the two he did with Dave Holland, but by Holland's own classic "Conference of the Birds," a masterwork on which Rivers' playing and influence can be heard vividly.