Johann Sebastian Bach spent the last part of his life in Leipzig, where he held between 1723 and 1750 the highly esteemed position of cantor at St Thomas' Church. This function chiefly required the composition of church music. Bach's production includes nearly 200 cantatas and the great Passion (St John, St Matthew) settings, as well as the Christmas Oratorio. In this musical context strongly influenced by the Evangelical Lutheran Church, the Mass holds a special position of its own. Throughout the history of Christianity, the Mass is the musical form that boasts the richest tradition. This "great Catholic Mass", as it named on the manuscript inherited by Carl Emanuel Bach, is Bach's only contribution for the Catholic mass. The composer considered his achievement as a contribution to interdenominational faith. Having reached the very end of his life, Bach endeavoured to sum up all his compositional mastery in this work. He wanted to leave a musical legacy for future generations, a kind of culmination of all his production. As well as composing new parts for this Mass, the musician also made use of previously composed music, which he reworked for the occasion. This was perfectly consistent with the practice of "parodies" in use at Bach's time. Despite the disparity of the musical material and the variety of forms and stylistic figures that are at once archaic, traditional or more modern for the time, Bach managed to create a vocal cycle of great expressive power. The many ornate choral fugues attest the work's great contrapuntal density. The instrumental parts also present an unusual design. The Mass in B minor is a "concertante Mass" in the sense that its musical value also shows in the orchestral part, unlike a capella works or those with a simple accompaniment, where the emphasis is on the vocal parts. Apart from their baroque splendour and highly developed writing, the instrumental parts of Bach's Mass in B minor also have their own expressive strength and contribute to the intention of this work that wholly responds to the Divine Order.