When looking at Mozart Operas, what does the "K" stand for, as in Don Giovanni, opera, K. 527: Notte e giorno

90% of the time it's a catalog reference, who cataloged it, performed it or indexed it by number, name and artist.

apparently the K here is for Köchel-Verzeichnis

here:

http://en.wikipedia.org/wiki/Don_Giovanni

and:

http://en.wikipedia.org/wiki/List_of_compositions_...

then:

http://en.wikipedia.org/wiki/K%C3%B6chel-Verzeichn...

it just goes on on on... :D

of course catalogs, indexes and references get lots or modified over the years so watch out if you want a particular piece you have to really, really be anal and careful.

The Baron "Kochel" -- the 19th century writer who catalogued Mozart's work.