The "guan" consist of a short cylindrical tube made of hardwood in northern China, where the instrument is called "bili". In the Guangdong region of southern China, it is made from bamboo and is called "houguan" (literally "throat guan"). It was originally used by street vendors but became incorporated into the Cantonese opera orchestra beginning in the 1920s. By the 1950s it had become popular throughout Guangdong and larger sizes were developed. Hardwood guans use and require a hard reed, whereas bamboo guans normally use a soft reed (however, sometimes a different hardness is used to change the timbre.)