Elvis Costello, that serial-collaborating load of middlebrow bloat, has failed to ruin Diana Krall, that impeccably tasteful piano-and-standards mood setter. In fact, The Girl in the Other Room -- on which Costello shares credit for seven songs -- finds Krall at a peak. Her transformation from diligent interpreter to semi-confessional singer-songwriter has resulted in material well worth the attention of future diligent interpreters. The four delicate originals that close the disc may not be jazz, but they're strong, subtle and both adult and contemporary -- words that desperately need to be reclaimed from radio. Good as these are, Krall is daring and elegant throughout, offering marvelous covers of Joni Mitchell, Mose Allison, Tom Waits and others. These are important because the new material might take some time to sink in. But once it does, you'll sink into it.