"The guitar zither (also chord zither, fretless zither, mandolin zither or harp zither) is a musical instrument consisting of a sound-box with two sets of unstopped strings. One set of strings is tuned to the diatonic, chromatic, or partially chromatic scale and the other set is tuned to make the various chords in the principal key of the melody strings.
First patented May 29, 1894 by Friederich Menzenhauer (1858-1937), the guitar zither came into use in the late 19th century and was widely mass-produced in the United States and in Germany by Menzenhauer and later by Oscar Schmidt Inc., the Phonoharp Company, and others " - (en.wikipedia.org 17.05.2022)
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