The marriage of Elvis Costello and Diana Krall had to be one of the more bizarre celebrity couplings of the past decade. Wildly creative New Wave icon hooks up with wildly conventional Shirley-Horn-ripoff-artist? Whatever works.A perhaps equally unlikely matchup of a strictly musical nature will occur tomorrow night at the Triple Door when Krall’s longtime guitarist Russell Malone (at left) plays duo with Bill Frisell.Seattle-based Frisell makes a habit of collaborating with all kinds of interesting players, from those on the progressive jazz tip, to world music greats, to old-timey experimentalists like Danny Barnes. I can’t recall him ever doing a serious joint effort with someone as totally mainstream and straight-ahead as Malone, a total hollow-body Wes Montgomery type of guy. Frisell’s elusive, warbly style seems fairly at odds with the clarity and in-the-pocket swing of modern bebop. Could be an interesting meeting of opposites.