According to legend, the instrument was invented in China during the dynasty. It is an important instrument in the Beijing opera orchestra, often taking the role of main melodic instrument in lieu of the bowed string section.
A similar Japanese instrument, called the ''gekkin'', was formerly used in Japan. Another very similar instrument, called ''&'' or ''đàn tứ'', is occasionally used in Vietnam.
The yueqin in China has 4 strings, tuned in 2 "courses" of A and D. Instruments used with the Beijing Opera, however, have only 2 single strings.
The frets are arranged rather like those on a mountain dulcimer, so that the instrument is diatonic .
The strings on the traditional form of the instrument are made of silk and plucked with a rather long, sharp plectrum, which is sometimes attached to the instrument with a piece of cord.
There is no sound-hole, but inside the sound box are one or more strands of wire attached only at one end, so that they vibrate, giving the instrument a particular timbre and resonance.
There's no bridge or saddle; the strings are simply attached to the anchor at the base of the instrument.
Modern forms of the instrument have 3 or 4 strings of steel each tuned to a different note. They're attached to the anchor by looping them through their own end-loops.
Three-string instruments are often tuned A D a, and four-string instruments are often tuned to A D a d.
The anchor on modern instrument may have up to 5 holes, so it can be strung and tuned as a 3- or 4-string instrument. The nut, at the peghead end of the instrument, is filed with notches appropriate to the number and position of the strings.
Modern yueqins are often played with a guitar pick.
* from The Musical Instruments E-book