Carl Philipp Emanuel Bach was one of the 18th century’s great musical rebels, working in a revolutionary and transitional period but destined to be overshadowed by others. History has a way of doing that to composers who don’t fit neatly into boxes. His father Johann Sebastian Bach and Mozart, geniuses both, perfectly reflect their times. Emanuel Bach may have been just as gifted, but he is neither Baroque fish nor Classical fowl and only now, it seems, are we really beginning to recognise his unique talents. Eschewing the single-emotion-per-movement model of his father’s generation, he revels in veering from one mood to another, juxtaposing introspection with temperamental outbursts and exploring divergent rhythms and quirky harmonies. Revered by Mozart, this is music that at times reaches beyond Classicism into the turbulence of Beethoven and the Romantic period. In short, CPE Bach was quite a visionary.

There are four Sonatas here, the first dating from 1744 (Emanuel’s most radical period) while the latest work, a Fantasie, dates from 1787, the year before he died. The early F-Sharp Minor Sonata begins with a highly unsettling movement, playing off an unstable rhythmic motive against an endearing gallant tune. His kaleidoscopic treatment of...