In Stockholm or Helsinki at this time of year, the sun sceptically peeps over the horizon in mid-morning, hovers at roof level for a while and hurts your eyes with its chilling glare, then succumbs to exhaustion and slumps out of sight in early afternoon. The climate induces affective disorders: a hunched gloom and a sozzled dream of distant spring. Music defines a country's emotional temperature, and two new recordings by Nordic singers - the Swedish mezzo Anne Sofie von Otter and the Finnish soprano Karita Mattila - explore the internal life of a region where the seasons are schizophrenic and nature takes on a polar abstractness, alternately dark or emptily bright.
Von Otter, accompanied by the pianist Bengt Forsberg, has collected unfamiliar songs by Swedish composers; Mattila, with the City of Birmingham Symphony Orchestra conducted by Sakari Oramo, concentrates on better-known works by Grieg and Sibelius. Although he was Finnish, Sibelius mostly used texts by Swedish poets, adopting the language of the conquering, occupying country. Finland's long period of servitude con-tinues to rankle, which is why Mattila cheekily calls herself a Slav not a Scandinavian. She reverts to Finnish for "Luonnotar", in which Sibelius set an excerpt from the epic Kalevala describing the creation: a hovering bird inseminates the waters, which bring forth the egg that contains our world. Apologising perhaps for Swedish imperialism, von Otter includes a buoyant shanty by Gustaf Nordqvist that became an unofficial anthem for Finnish independence.
The clever title of von Otter's disc is Watercolours, which captures exactly the favoured terrain of the songs - dazzling sky and sea, merged by the wash of light - and the bleached tonality of her voice. In a cycle of lyrics composed by Gunnar de Frumerie, erotic bliss does not seek refuge in darkness: the lover's closed eyes see a blinding light. Gosta Nystroem, an inveterate sailor who explored the Baltic in fishing boats and canoes, celebrates a purged, laundered marine landscape. "How can anyone," he asks, in a song about a drowsy sea, "contemplate evil deeds?" On the cover, von Otter herself, nunnishly swaddled in white wool, broods beside a cold green ocean - as if, like Ibsen's lady from the sea, she is about to return to the element from which she once emerged.
The great performance here shuts out nature, since it takes place in a stifling, hermetic sickroom. Four songs by Bo Linde set poems in which Harriet Lowenhjelm chronicles the advance of the tuberculosis that killed her. Von Otter's vocal acting turns these short, painful pieces into something like a condensed Scandinavian version of La Traviata, with every detail of the disease starkly registered. The voice is at first hollow, almost tuneless, lacking the breath or energy for song; it swoons light-headedly, or expels words in what is almost a cough. Begging for the gratification of death, she mews or hums, since the inarticulate sound alone can convey her abject appeal. The last song in the group has a text written by Lowenhjelm in English rather than Swedish. It describes her happy reconciliation to her end, and its sentiments are so austerely imper- sonal that they could perhaps be ex-pressed only in a foreign language, which estranges the dying writer from her former existence. She already inhabits the undiscovered country.
If von Otter is a delicate, intimate watercolourist, Mattila hurls pigments around with the glorious abandon of a great painter. However, her sound is haunted by an undertone of darkness; a guttural catch in the voice further down allows her to plummet from jubilation to melancholy. Appropriately, the two most substantial pieces on Mattila's disc are vocal tone-poems by Sibelius, orchestral pictures of desolate or agitated landscapes. "Autumn Evening" describes a wanderer exhilarated by characteristically filthy weather: clotted clouds presaging a storm, with a seagull screaming as the water turns choppy. The orchestra subterraneously grumbles, or emits gruff sustained harmonies. A faintly reverberant drum makes the rain audible.
Mattila plucks exposed high notes from the air, and her vocal daring vouches for the spiritual courage of Sibelius's pantheism, which finds nature to be worthiest of worship when it is at its bleakest. "Luonnotar" is even more thrilling. Skittering strings portray the ferment of uncreated nature. The voice swoops and plunges as it describes the teal that nests on the nursing waters, or keens as the universal mother's limbs convulse. When the egg cracks at the end, its mottled white matter splashes the sky with stars; Mattila, whose voice rhapsodises over these wonders, shines up there among them.
Stepping across the border into Norway, she also sings Grieg's lovable "Spring", which surveys the resurgence of nature but concludes by wandering off into a disconsolate minor key and surrendering to sadness. Writing in balmy Italy, Shelley optimistically asked: "If winter come, can spring be far behind?" Further north, spring's belated arrival merely announces the imminence of winter.
Anne Sofie von Otter and Bengt Forsberg appear at Wigmore Hall, London W1 (020 7935 2141) on 4 April. Watercolours is available from Deutsche Grammophon. Karita Mattila's album of Grieg and Sibelius songs is released by Warner Classics in May