Amy Macdonald herself is a curious thing, an adult alternative singer/songwriter operating in a netherworld between indie and the mainstream.

Naturally, she edges toward the mainstream -- the polished production has a way of sanding down any edges -- but her throaty growl gives this a heart unruly enough to prevent A Curious Thing from flowing too easily.

Subtract Macdonald’s passionate vocals from the equation and A Curious Thing flows plenty easily, its surfaces gleaming with precision and its melodies sweetly lilting whether it’s a ballad or an understated folk stomp.

If the production is the clearest signal that Macdonald is gunning for a larger crossover audience with her second album, her songs also show some signs of a swift sophomore sequel -- she writes about her brushes with fame just a bit too often and bluntly, an affectation that doesn’t wear well no matter how well-executed the music is.

These acknowledgments of Macdonald’s burgeoning European fame hinder A Curious Thing but don’t detract from its essential appeal as soft and shiny AAA pop with a bit of a thumping heart.