Few albums in the ECM catalogue have proved as surprising, as successful or as enduring as Officium, the landmark meeting of saxophonist Jan Garbarek and the celebrated early-music vocal quartet The Hilliard Ensemble. Recorded in the resonant acoustics of the Propstei St. Gerold monastery in Austria, the project sets Garbarek improvising freely around medieval and Renaissance sacred music, from Gregorian chant to the polyphony of composers such as Pérotin and Cristóbal de Morales. The four voices of the Hilliard Ensemble sing the ancient lines with the purity and precision for which they are renowned, while Garbarek's soprano and tenor saxophone weaves above, around and between them like a fifth, wordless voice, sometimes shadowing the melody, sometimes soaring off into keening improvisation. The vast natural reverb of the monastery becomes an instrument in itself, blurring the boundary between the centuries-old music and Garbarek's contemporary interventions. The effect is at once meditative, otherworldly and deeply moving, music that seems to exist outside of time.

A genuine cross-over phenomenon that reached far beyond the usual jazz or classical audiences, Officium remains a singular and unclassifiable achievement, and one of the most beloved recordings the label has ever released. It spawned two equally admired sequels, Mnemosyne and Officium Novum, but the original remains the purest distillation of the concept. On vinyl, the cathedral-like reverb and the interplay of voices and saxophone are rendered with extraordinary depth, an essential acquisition for anyone drawn to sacred, ambient or genre-defying music.