On May 30, 1790, Mozart wrote a testimonial for the young Eybler: "I, the undersigned, attest herewith that I have found the bearer of this, Herr Joseph Eybler, to be a worthy pupil of his famous master Albrechtsberger, a well-grounded composer, equally skilled at chamber music and the church style, fully experienced in the art of the song, also an accomplished organ and clavier player; in short a young musician such, one can only regret, as so seldom has his equal."