German organist and composer who was one of the first musical lexicographers.

In 1702 Walther was organist at the Thomaskirche at Erfurt, in 1707 organist at Weimar, and from 1721 court musician there. Between 1708 and 1714 he formed a friendship with J.S. Bach, of whom he was a second cousin. Walther's compositions, which were highly respected by his contemporaries, include chorale preludes and variations for the organ, and organ arrangements of concerti by Tomaso Giovanni Albinoni, Giuseppe Torelli, and other Italian composers. His Musicalisches Lexikon, completed in 1732, was the first music encyclopaedia of biography, bibliography, and musical terms. It remains an invaluable work in the study of Baroque music.