Butter and pork, folksong and psalteries and Kalevala and Corelli were on the bill of fare for the lunchtime Prom marking the 100 years since Finland's Declaration of Independence – and without a single note of Sibelius.

Väinämöinen, the mythic bard of the Kalevala, created order out of chaos by his magical runic singing and playing. He crafted a kantele, a kind of psaltery or lap harp, from the bones of a pike which he first cooked and ate. In harp and kantele player Andrew Lawrence-King’s 2016 work Kalevala: the Opera, from which two scenes are performed tonight, the bard decries, “Let everyone come and listen, those who maybe never heard before the joy of the eternal rune-songs, the sound of the kantele!” The folk story has it that the wind blew Väinämöinen’s song to Kaustinen, on the north-west coast of Finland. Kreeta-Maria Kentala, the violinist of the ensemble for today’s Prom, is a board member of the Kaustinen Folk Music association. Work by her maternal grandfather, Viljami Niittykoski, was included in the programme, and the soprano Anu Komsi has family connections in the region too. There, folk music is kept alive and fresh by being passed down through the family and by travelling musicians, often seasonal farm workers, playing at weddings. The hauntingly beautiful song “Kanteleeni” was composed by Finland's first professional female musician, Kreeta Haapasalo, who was driven off the land by agricultural famine in the 1860s. The travelling roots of the musicians was well exemplified by the harmonium, played by Milla Viljamaa and inengeniously packed in its own integral, wheeled flight case.

The programme, with compositions ranging from 1582 to 2016 (though some stemming from much earlier sources) opened with one of two songs from the Piae Cantiones – the first printed Finnish music, fervently sing in Latin by Komsi. The distinctive humming, plucking and strumming of the harmonium, fiddle and theorbo ensemble was immediately ear-catching. The songs were interspersed with the two scenes from Lawrence-King’s Kalevala: the Opera. The trochaic metre and alliteration of the text, familiar from Sibelius’ Kullervo and Luonnotar, with their imagery of a nectar-sauna, swans and the dark forest realm of Pohjola, were seasoned by the Baroque rhythms and spikiness reminiscent of Vivaldi along with Anu Komsi's pungent soprano.

The sets of songs were intermingled with traditional instrumental polkas, waltzes and marches from Kaustinen, which are often performed at three-day wedding celebrations and played with rustic robustness and rhythmic bounce. Here the irrespressible Anu Komsi, dressed in folk costume, danced around the platform with her own triangle obbligato.

A central set of traditional folk sungs varied between the elegiac, sorrowful and patriotic, while in the raucous Ookkos syöny sianlihaa (“Have you eaten pork, then?”) the harmonium player and violinist joined in with the chorus. The final set sung by the soprano included the single evocative Swedish setting and Niittykoski’s exquiste Joutsenet, with its rippling accompaniment and imagery of flowers and flights of soaring swans. The last piece was Lampaan polska ('La Folia') where Corelli’s variations on the well-know bass theme somehow found their way into the local music of a remote corner of Finland. The violinist, an accomplished Baroque player, managed to transmute the theme into a Finnish folk dance with her technique and range of colour, while nonsense verses sung by the unquenchable, exuberant soprano were superimposed.

During the encore, the ensemble – for which Anu Komsi took up the fiddle – played the traditional A major March, as Lawrence-King explained, was actually in D. The piece provided final proof of the heritage, vitality and continuing inventiveness of Finnish folk music, as delivered by this talented group of musicians.