The Mass in B minor is a musical work composed by Johann Sebastian Bach (BWV 232), for two sopranos, a contralto, a tenor, a bass, a choir and an orchestra. The Mass in B minor is essentially composed of an assemblage of various pages drawn from various previous works of the composer and rewritten by him according to the process known as parody (in the old sense of the term: "text composed to be sung on a known music "1): for example, the cantata BWV 12 provided the material of the Crucifixus, the Hosanna is taken from the cantata BWV 215, the Agnus Dei comes from the oratorio of the Ascension BWV 11. Only a third about the work consists of "original" compositions. Parody is a relatively common process for Bach, as was the case with many composers of the time, as it was often the only way to rehearse plays that their authors felt were particularly successful. The tone of B minor, as is the custom, comes from the first piece (Kyrie eleison), the other numbers being, with the exception of No. 26 (Agnus Dei in G minor), in the neighboring tones, particularly in the relative major D range (13 out of the 27 numbers). Source: Wikipedia.