Joseph Yasser (April 16, 1893 – September 6, 1981) was a Russian–American organist, music theorist, author, and musicologist.
An influential figure who established a handful of musical institutions, Yasser is noted for his 1932 publication, A Theory of Evolving Tonality.
[6] In 1919 he was named chief organist of the Imperial Opera (Bolshoi Theatre), and in 1920 and 1921 toured Siberia with a state quartet as a pianist and lecturer.
[10][11] In a series of articles from 1937 to 1938, which were later compiled into a book titled Medieval Quartal Harmony, published by the American Library of Musicology, he proposed the implementation of a system "harmonizing pentatonic melodies" based upon the perfect fourth interval.
[5] According to protégé Herman Berlinski, in his final years Joseph Yasser was a "recluse" who avoided prolonged periods outdoors due to an anaphylactic reaction to a wasp sting which he experienced in the early 1960s.