His studies took place at the Johann Wolfgang Goethe University and Technische Universität Berlin with Carl Dahlhaus (master's degree examination in 1982).
From 1982 to 1985, he was a scholarship holder of the Volkswagen Foundation in Parma and Paris, and in 1985, he received his doctorate at Technische Universität Berlin.
In 2006, he declined the call to the professorship for theatre studies at the University of Bayreuth combined with the direction of the Forschungsinstitut für Musiktheater in Thurnau castle.
His publications on Verdi are numerous, dealing not only with analytical questions but also with the social history of Italian opera and the composer's biography.
With a conference organised in Bern in 1996, the contributions to which appeared in print in 2000, Gerhard was among the first music historians to address the involvement of German musicology in the Nazi regime.