Rímur brings together the three singers of Trio Mediaeval and the Norwegian trumpeter Arve Henriksen in a programme of chants, hymns, folk songs and improvisations drawn from Icelandic, Norwegian and Swedish sources. Henriksen had often joined the trio in concert, but this is their first extensive collaboration on disc. The title refers to the Icelandic rímur, rhyming verses handed down orally from one generation to the next.

The voices are those of Anna Maria Friman, who also plays Hardanger fiddle, Linn Andrea Fuglseth, who adds shruti box, and Berit Opheim. Most of the music took shape over several summers by the Dalsfjorden on the Norwegian west coast. The hymns were arranged by the quartet together, many of the folk songs by Friman, others by Opheim and Fuglseth. The album was recorded in February 2016 at the Himmelfahrtskirche in Munich-Sendling, with Peter Laenger as engineer, and produced by Manfred Eicher. It is the trio's seventh album for ECM.

Three hymns to Nordic saints form the backbone of the sequence: Birgitta of Sweden, Magnus of Orkney and Sunniva of Norway. Rosa rorans bonitatem, by the fourteenth-century Swedish composer Nils Hermansson, opens the album, with the trumpet first moving in step with the voices and then breaking away. Henriksen often plays with the mouthpiece removed, a breathy sound that one reviewer compared to the Japanese shakuhachi. The Norwegian wedding tune Brureslått is sung without him, and its stillness stands out in the sequence. Krummi is a new piece by Friman and Henriksen. Tyran Grillo of ECM Reviews counted it among the highlights, together with the anonymous chant Alma Redemptoris Mater.

Writing in Jazz Views, Nick Lea called it "a beautiful recording" that might bring the trio a wider audience. He set it beside the long partnership of the Hilliard Ensemble and Jan Garbarek. Peter Bacon of London Jazz News heard Henriksen's horn acting "like a fourth voice, its different timbre adding new colour" (2017). For Günther Huesmann on Südwestrundfunk, the album was a masterpiece of mutual empathy, with medieval monophony turned into new polyphonic settings.

This is the CD edition, ECM 2520, first released on 3 March 2017, with a performer's note by Anna Maria Friman in the booklet.