Kjølvatn is the first ECM album by the band of Nils Økland, the Norwegian master of the Hardanger fiddle. His earlier ECM records were the solo Monograph, the duo programme Lysøen and the distorted drones of Lumen Drones. Here he leads a quintet whose members move between folk music, jazz and contemporary classical music. The music is quieter than Lumen Drones, built from Økland's sketches and shaped by the whole group.

Økland plays Hardanger fiddle, violin and viola d'amore. With him are Sigbjørn Apeland on harmonium, his partner on Lysøen, the bassist Mats Eilertsen, Håkon Mørch Stene on percussion and vibraphone, and Rolf-Erik Nystrøm on alto and baritone saxophones. Most of the ten pieces are his, while the arrangements are credited to the band. Økland links this way of working to early baroque practice, where a sketch was the basis for making new music. The album was recorded in June 2012 in Hoff Church at Østre Toten, a stone church near Lena known for its acoustics. Audun Strype engineered the session, with Manfred Eicher as executive producer.

The stone room is part of the music, and the slower pieces leave space for its resonance. The title track sets a lyrical violin melody over subtle drones, cymbal washes and pizzicato bass. Puls, at over eight minutes the longest piece, which ECM credits to Økland with Eilertsen and Stene, rests on insistent drumming and low bass, with Økland's bowing floating above. Blå harding shares its title with his 1996 debut album, and Amstel closes the set with bird-like saxophone answering a plaintive fiddle line.

In the Evening Standard, Jane Cornwell found that pieces such as Start, Drev and Puls have "a quiet, often startling beauty", with plucked chords, floating drones and edgy dynamics around Økland's bowing. Gary Whitehouse of Green Man Review heard music that often sounds ancient, drawing at times on folk sources and at times on early baroque, always with a Nordic feel. For Tyran Grillo of ECM Reviews, the record "rarely bubbles beyond a simmer, but its flavors are all the purer for it."

This is the CD edition, ECM 2383, first released in 2015.