Joseph Eybler (Joseph Leopold Edler von Eybler to give you the full name) belongs to that unfortunate group of composers who were popular and musically influential while alive but have vanished from the spotlight to become mere historical footnotes. Although Eybler showed early promise as a pianist, he began studying law. However, the family’s fortune was lost when their home burned and it was necessary to abandon law studies and earn his way as a musician. He studied under Albrechtsberger (teacher to Beethoven and Hummel) and Joseph Haydn, to whom he was distantly related. Through Haydn, Eybler met Mozart, who offered further musical instruction. Mozart was so impressed with Eybler’s skills that Eybler assisted with coaching the singers in, and later conducting performances of Cosi fan tutte. Mozart’s widow, Constanze selected Eybler to complete the Requiem after her husband’s death. Speculation continues to surround Eybler’s contribution to the Requiem.
In 1789, a performance of "Messiah" that was to have a radical effect on the course of the oratorio's performance history was given in Vienna. Baron Gottfried Van Swieten, who later translated and edited the text for Haydn's "Creation", had, as a diplomat in London during the late 1760s, become an ardent Handelian. Among other Handel scores, he took back to Austria a copy of the first edition of the full score of "Messiah", published by Randall and Abell in 1767. Beginning with "Judas Maccabaeus" in 1779, he introduced works by Handel into the annual oratorio series given for the benefit of the Tonkunstler Society, a Viennese musical charity. In 1789, he presented "Messiah" and, for this Viennese premiere, commissioned Mozart to fill out the accompaniments, largely dispensing with keyboard continuo and replacing the tromba parts practically unplayable for late 18th century trumpeters.