Frost is Aggie E. Peterson and Per Martinsen, aided in part by fellow Norwegian duo R?yksopp. No work is quite as animated as R?yksopp’s apex, “Eple” (though the tightly wound clickhouse spring of “Running Boy” nears in approach), but that amount of distraction wouldn’t complement Peterson’s Dido-ish vocals, which benefit from a gently flowing, multi-hued wrap of crystalline tones. A song such as “Half-Whole” uses melodic chords as delicate and wavering as the skin of a wind-rippled reflecting pool. Martinsen’s beats are more straightforward, calculated blip-pop (popular to listeners of Morr Music), and allow Peterson’s effervescent vocals a pane on which to condense. Melodica encapsulates the comfort of a sweater-weather keeper.