Johann Gottfried Walther (1684 – 1748) was a German music theorist, organist, composer, and lexicographer of the Baroque era.
Walther was born at Erfurt. Not only was his life almost exactly contemporaneous to that of Johann Sebastian Bach, he was the famous composer's cousin.
Walther was most well known as the compiler of the Musicalisches Lexicon (Leipzig, 1732), a dictionary of music and musicians. Not only was it the first dictionary of musical terms written in the German language, it was the first to contain both terms and biographical information about composers and performers up to the early 18th century. In all, the Musicalisches Lexicon defines more than 3,000 musical terms; Walther evidently drew on more than 250 separate sources in compiling it, including theoretical treatises of the early Baroque and Renaissance.
The single most important source for the work was the writings of Johann Mattheson, who is referenced more than 200 times.
Johann Gottfried Walther was an important German organist and composer. His first organ lessons were in Erfurt with Johann Bernhard Bach, and he quickly became an able child singer. When he was 18 he landed his first organ post, at Erfurt's Thomaskirche.
After a flirtation with philosophy and law at the local university, Walther turned all his attention to music, becoming especially interested in music theory. He began touring Germany on a regular basis, and in his travels he met the important theorist Andreas Werckmeister, becoming one of his protégés, if usually by long distance.
In 1707 he obtained his first and only "real" adult job, organist at Weimar's Stadkirche; there he remained for the rest of his life, another four decades.
He also served as music teacher to Prince Johann Ernst in Weimar, to whom he would dedicate his 1708 treatise, Praecepta der musicalischen Composition. In 1721, he added the duty of heading the ducal orchestra.