This Canadian duo has achieved major success on the folk-pop circuit by simple means: nice melodies, tight harmonies, and a warm and approachable style.

On their fifth album, however, that style starts getting dangerously close to gauzy -- and if they aren't careful, they run the risk of becoming insubstantial.

The problem isn't that their lyrics are shallow; their songs mostly deal with predictable subjects (first love, social cliques, romantic bemusement) but they do so fairly elegantly and at times they make artful use of genuinely startling and slippery imagery ("Virginia Woolf," "Peggy").

The problem is, first of all, that almost every song on Best Day is soporifically slow and quiet, and second, that both their sound and their songs' messages sometimes border on childishly simple: the slightly off-key piano that plinks around on "Lennon & McCartney," the junior-high yearbook philosophy of "Best Day," the stacked cliches and enervated Indigo Girls vibe of "Life on Earth." There are moments when this approach works very well (such as on the whisperingly lovely "Still Life") and there are moments when the energy level rises nicely (such as on the gently swinging "Great Escape").

But those moments are a bit too few and far between.