With world music bands, the presence of Western guest stars usually bodes ill. All that fine talk of cross-cultural influences is seldom more important than the strategy of cross-marketing. But on Tassili, the presence of Wilco's Nels Cline, various members of TV on the Radio and the Dirty Dozen Brass Band doesn't actually detract from the sound of Tinariwen, the celebrated musical semi-nomads from the southern Sahara. Aside from a few snatches of lyrics in English, the guests are unobtrusive. They make themselves scarce. The real change from previous CDs is the choice to move from spiky electric guitars to spiky acoustic instruments. Unchanged is the core of Tinariwen's sound, based on call-and-response singing and a deep bluesy groove that John Lee Hooker would have appreciated.