It has been a while since we reviewed Haydn's music from the first half of the decade. Now that we are entering the 19th century (or, if you would quibble, at least we can agree on the 1800's!), it would be appropriate to look at his production from 1796-1800.
While this half of the decade didn't compare in quantity, the quality is far more than adequate to make up for it. There are some new or different genres, but the music produced in the existing genres, which should have been worn thin by now, was in fact among the best he ever produced, and as Charles Burney wrote to him about the Op. 76 quartets:
I had the great pleasure of hearing your new quartetti (opera 76) well performed before I went out of town, and never received more pleasure from instrumental music: they are full of invention, fire, good taste, and new effects, and seem the production, not of a sublime genius who has written so much and so well already, but of one of highly-cultivated talents, who had expended none of his fire before.
Landon – Collected Correspondence &c.
Haydn's Music of 1791 - 1795
Haydn's Music of 1796 - 1800