Johann Wilhelm Hässler was a German musician who performed as an organist, keyboardist, and composer in numerous European cities before settling in Russia, where he was a renowned teacher and composer, in 1792. Born the son of a hatmaker in the central German city of Erfurt, Hässler apprenticed with his father while taking organ lessons with his uncle, Johann Christian Kittel, who was a pupil of Johann Sebastian Bach. By the age of 14, Hässler had progressed enough in his studies to be engaged as an organist at a church in Erfurt, the Barfüsserkirche. Hässler started composing for the keyboard in the 1770s, and traveled extensively as a performer in Germany in that decade and the one following. In his travels, Hässler became acquainted with the leading figures of the period. During a visit to Hamburg, Hässler met Carl Philipp Emanuel Bach, by whom he was much influenced. Toward the end of the 1770s Hässler published several keyboard sonatas. He married one of his students, singer Sophie Kiel, in 1779, and the following year they put on a series of public winter concerts in Erfurt. During a visit to Dresden in 1789, he lost to Wolfgang Amadeus Mozart in an informal keyboard contest; he apparently made a poor impression on Mozart, who penned an unflattering portrait of Hässler's skills as a contrapuntist and performer in a letter to his wife. Evidently Haydn held a higher opinion of Hässler's musicianship. When Hässler arrived in London in 1790, he quickly became successful as a performer and teacher and performed keyboard concertos under Haydn's baton. Haydn conducted a benefit concert for the composer before Hässler's departure for Russia in 1792. In St. Petersburg, Hässler was appointed pianist and teacher to Grand Duke Alexander in 1793, and the same year composed a cantata for his patron's wedding to Princess Elizabeth. Hässler set up a music publishing business in St. Petersburg, which he turned over to his partner some time after he moved to Moscow in 1796. Most of Hässler's own music, which mainly consisted of keyboard compositions, was published in Russia. He spent the last two decades of his life in Moscow, where he was eagerly sought out by the new generation of native Russian composers, who would go on to play an active role in shaping Russian music after decades of ceding prominence to foreign composers.