Some famous composers were notorious perfectionists—and then there was Johannes Brahms, the Perfectionist of Perfectionists. He spent 14 years tinkering with the score of his First Symphony, remember.
Brahms once claimed he had written and discarded twenty string quartets before publishing his first two in the year 1873. To say Brahms was his own severest critic would be putting it mildly, but there was one other person whose opinion Brahms valued above all others, and that was Clara Schumann, one of the finest pianists of her day, the widow of his mentor Robert Schumann, and a fine composer in her own right.
So it comes as no surprise that the Third String Quartet of Brahms, the Quartet in B-flat Major, published as his Opus 67, was first performed as a kind of "test run" at the Berlin home of Clara Schumann on today's date in the year 1876. The performers were the famous Joachim Quartet, led by violinist Joseph Joachim, a long-time friend of Brahms.
Apparently Clara and Joseph liked the new quartet, but Brahms arranged for one more trial run the following month, and probably tinkered with the score right up to its first public performance by the Joachim Quartet in Berlin on October 30, 1876.
Brahms had composed his Third Quartet the previous summer, while on vacation, and unlike his preceding two string quartets, both austere and introspective works, this one was light-hearted and cheerful—"a useless trifle," as Brahms himself put it, adding it was just his way to (quote) "avoid facing the serious countenance of a symphony."