The guqin is nearly always used a solo single instrument, as its quietness of tone means that it cannot be heard over the sounds of most other instruments or an ensemble. It can, however, be played together with a "xiao" (end-blown bamboo flute), with other qin, or played while singing. In old times, the "se" (a long zither with movable bridges and 25 strings, similar to the Japanese koto) was frequently used in duets with the qin.