Enlisting the help of producer/boyfriend Stephan Jenkins (of Third Eye Blind), the 24-year-old Vanessa Carlton is trying to show us that she's matured since 2001's Be Not Nobody. Singing about unicorns in ''Half a Week Before the Winter'' does not help her cause. Amid the dippy Dear Diary lyrics and gratuitous string sections, however, there are a few treasures on Harmonium: ''Afterglow,'' ''Papa,'' and the catchy single ''White Houses'' suggest Carlton's melodies might stand a chance on their own.

