An important part of Baudouin de Jaer's compositions are his compositions for Geomungo Solo.

The Geomungo, zither of the Kingdom of Goguryeo, sometimes called "black zither" is one of the oldest Korean instruments. We find the first traces of it in the 4th century of our era as a sacred instrument exclusively used in ritual court music. Over the centuries, the instrument slips into the middle-class houses, magnificently accompanying the games and poetic songs, deploys its strength in solo play as well, until becoming inevitable in the great ensembles of shamanic tradition of the southwest. Geomungo is a very complete instrument in Korean aesthetics. It combines delicate softness with brutal force and makes it possible to express wonderfully the contrasts of nature. Of the six strings stretched on the soundboard, only two, daehyeon and yuhyeon are melodic. The strings are struck in the right hand by a bamboo stick, the suldae, which percussively punctuates a game of return between force and suppleness, while the left hand vibrato varies the tension of the rope played. (...)

Jacques-Yves Le Docte, introductory text in the libretto of the CD "Baudouin de Jaer: Geomungo and Gayaguem compositions VOL I / 2013"