Never before have conditions been so favourable for writing a handbook on the Mass in B minor. First, the prospective author has the benefit of over a century of critical writing. Secondly, so many fundamental source problems have been solved in the last thirty years – e.g. the chronology of Bach's work on the manuscripts, and the origin of some of the parodied movements – that one can avoid many of the mistaken suppositions with which such a large proportion of the literature is riddled.

On the other hand, research on the Mass has never before been such an exacting task. The enormous body of existing literature must be assimilated with an eye both to its errors and to its perceptions. Such are the persistent puzzles concerning the origins, function and quality of the Mass in B Minor that it is all too easy to rely on opinions and beliefs which ignore the historical anomalies. Even with all the discoveries of recent years, there is still much room for interpretation in assessing how the work relates to Bach's compositional career, how it stands in the practical, liturgical context of his time (both Roman Catholic and Lutheran), why Bach decided to extend the Kyrie and Gloria – the Lutheran Missa presented to the Elector of Saxony in 1733 – to a full setting of the Latin Ordinary in the last years of his life, how many of its movements are parodies, whether it was ever performed as a complete work or even as a Missa, and indeed whether it was designed with performance in mind in the first place.