Two of my favorite musicians share today's date as their birthdays — Clara Wieck Schumann and Arnold Schoenberg.
Clara (September 9, 1819 — May 20, 1896) wrote some of the most beautiful and enchanting music of the 19th century, from the authoritative Piano Concerto in A minor, Op. 7 to the aggressively melancholy Piano Trio in G minor. She was a fabulous piano player, taught by her father. Mr. Wieck also gave piano lessons to one Robert Schumann, who first encountered Clara when she was 12 years old. By 1837, Clara and Robert were engaged, and they were married in 1839. She didn't write much over the course of her 74 years, but she contributed greatly as muse to both her husband, Robert, and her husband's best friend, Johannes Brahms.
Brahms, of course, loved her intensely, yet Clara never reciprocated beyond the friendship she and Brahms shared, even after Robert's death in 1856. Of the many pieces Brahms wrote inspired by Clara or guided by her critical ear prior to publication, the second movement of Brahms Piano Concerto No. 1 in D minor, Op. 15 stands out. About the gorgeous adagio second movement, Brahms said, "I am making a gentle portrait of you in the form of an adagio."
Arnold Schoenberg (September 13, 1874 — July 13, 1951) is, in my humble opinion, one of the most intriguing characters throughout the history of classical music. Many either shudder or shriek with joy at the sound of his name; there is no in-between.
Perhaps classical music's most superstitious composer, Schoenberg predicted that, since he was born on the 13th day of a month, he'd die on the 13th day of a month, and he was correct.
Schoenberg's most notable contribution to the development of classical music came in the formation of the Second Viennese School and the eventual "emancipation of the dissonance" in his famous (or infamous, depending on your side) essay in 1926 called "Opinion or Insight?" In it, he chose to disregard the tonal, dominant/tonic training pervasive in all of Western music, which puts hierarchies on specific notes in a scale and key. Instead, Schoenberg created what he called "twelve-tone technique," in which all 12 notes in the Western scale are given equal significance.
He began as a late-romantic composer (listen to his one-movement string sextet Verklarte Nacht, Op. 4), but following the advent of twelve-tone music, abandoned tonality altogether. The way had been paved by composers like Claude Debussy and Richard Wagner, and Schoenberg simply took the final step. The Suite for Piano (1921-1923) was his first entirely 12-tone piece.