If you were a member of the European nobility, the summer of 1798 was a very anxious time. A rampaging French general named Napoleon Bonaparte had crushed your armies on land and now word had it his fleet had escaped a British blockade. The possibility that Napoleon would control both land and sea struck terror in many a nobleman's breast. To them, Napoleon was a revolutionary Boogeyman who would send them all to the guillotine.

During this anxious time for Prince Nicholas Esterhazy the Second, his favorite composer Joseph Haydn was at work composing a Latin mass he titled " Missa in angustiis" or "Mass in Time of Fear." It opens in the key of d minor, the same key employed by Mozart for the spookiest scenes in "Don Giovanni," an opera that had made a big impression on Haydn at its premiere in Vienna ten years earlier. As Haydn scholar H. C. Robbins Landon puts it, in 'Don Giovanni,' 18th century listeners were presented with "the presence of real fear — nay terror."

So, when word reached the rattled princes of Europe that the British Admiral Nelson had cornered and destroyed the French fleet, everyone breathed a huge sigh of relief, and, coincidentally, Haydn ends his Mass in the more optimistic key of D Major.

First performed on today's date in 1798, Haydn's Mass soon came to be known as the "Lord Nelson Mass," and in H. C. Robbins Landon's view stands as "arguably Haydn's greatest single composition."