Johann Georg Albrechtsberger
When Beethoven was a young man, he had some composition lessons from Joseph Haydn.  When Haydn was going to travel to England for several months, he asked Albrechtsberger to teach Beethoven while he was gone. These lessons took place from 1793 to 1795.  A few years later, Albrechtsberger said about Beethoven that “he learned absolutely nothing and will never accomplish anything decent”.  Beethoven said that Albrechtsberger was a “musical pedant”.  However, Beethoven still studied Albrechtsberger’s books on music theory.  The string quartets which Beethoven wrote near the end of his life show the influence of Albrechtsberger.