As the subtitle of this book suggests, no one can ever fully plumb the depths of the notion of “genius”. This, of course, does not deter people from trying. Witness this collection of essays, chronicling an academic career largely spent in seeking to understand what made or still makes these classical music titans, Bach and Mozart, so revered.

Robert Marshall, Sachar Professor of Music Emeritus at Brandeis University, starts by suggesting that the music of the 18th century should be viewed as a continuum, rather than divided into the customary “late baroque” and “classical” periods. He believes Bach and Mozart should not be seen as opposites; rather, as the fulfilment of two different lines of development, one coming from Protestant Germany and the other from the secular tradition of Italy.

From this point of departure Marshall takes up some interesting avenues of enquiry. What motivated each man to compose? In what way did their personal and family relationships shape their music? How did their compositional processes differ? What factors shape the latter-day performance of their music? What religious or societal factors were brought to bear on their compositions? What does the contemporary reception of their...