A choir on a CD of Brahms's fourth symphony? Easily explained: one aim of John Eliot Gardiner's illuminating Brahms symphonic cycle, recorded live at London's Festival Hall and now complete, has been to show the composer's debt to earlier baroque masters. Here, a selection of motets by Giovanni Gabrieli, Schütz and Bach are set alongside Brahms's own Fest- und Gedenksprüche Op 109 for unaccompanied double chorus. They provide a surprising context for the symphony, given in a transparent, analytical performance by the Orchestre Révolutionnaire et Romantique. Harmony and counterpoint gleam, with no aural smudges and not a jot of bookish didacticism.