Mozart    Vesperae solennes de confessore, K339

Mozart's youthful second and more frequently performed setting of the Vespers.

Haydn    Mass No. 12 in B flat : 'Theresienmesse'

In his mid- to late-sixties, Haydn wrote six great masses, for the Esterházy family, to celebrate the name day of Princess Maria Hermenegild, the wife of Prince Nikolaus II.  This is one of four in the key of B flat, in this case the key reflecting the instruments at Haydn's disposal at that time.