Mozart mentioned in a letter to his father that he wanted to write a mass for his new wife Constanze, who was a soprano. “But there was no commission,” says Temple University music history professor Steven Zohn. “It’s not usual for him to write something on spec or just because he wanted to write something that showed the love for his wife.”
Also unusual for Mozart’s time was the musical style. The work is a "cantata mass" where choruses alternate with elaborate arias.
“You have these very solemn choral movements” says Zohn. “Then you have something that sounds like it could come out of The Magic Flute or something with the Queen of the Night singing!”
There are also fugues and double fugues—more reminiscent of Bach and Handel than late 18th-century composers.
Mozart never wrote all the sections needed for a mass, and the first performance—with Constanze as soloist at the Abbey of St. Peter’s back in Salzburg— may have used supplemental music. Yet even in its unfinished form, says Zohn, "The music is Mozart at his most dazzling. You get Mozart the opera composer, Mozart the composer of sacred vocal music, and Mozart the explorer of Baroque counterpoint...all wrapped into one.”
Mozart’s Mass in C minor, published soon after the composer’s death, is now a standard part of the concert repertoire.