Xi-u Xi-u is a double-reed aerophone of H'mong people, a minority living the Northern Vietnam.

Xi-u comprises 4 components including body, bell, stake, and reed. The body is a cylindrical hollow hard-wooden tube of 25 cm length. There are 8 fingering holes, of which, 1 hole is located at one side of the body and near the reed stake, and the 7 other holes are vertically arranged in equal distance at the front side of the body. The pyramid-shaped bell is made from brass. The reed stake is made from metal while reed is made from goose feather.

When playing Xi-u, instrumentalist holds in his mouth the whole reed, and takes breath at his nose and breathes out at mouth forcing air into the reed. By such a blowing way, the instrumentalist can play for hours without breaking-off of his breath. Sound range of Xi-u consists of 2 octaves including Do (perfect) - Re (tender) - Mi (tender) - Fa (hard) - Sol (perfect) - La (tender) - Si (tender) - Do1 (perfect). The techniques applied to playing Xi-u vary from this musical piece to another piece but usually consist of tongue techniques like flutter-tongue, tongue articulation, and glissando.

Xi-u is the instrument exclusively for men played in ensemble with other instruments in customary rituals of H'mong community.