24, based on the 12 tone equal temperament scale, with all the intervals being semitones. There is also a need to standardize the tuning when the instruments are played in an orchestra, which in turn may also affect how the instrument is made. For example, traditionally dizi is made by using a solid piece of bamboo which made it impossible to change the fundamental tuning once the bamboo is cut. This issue was resolved in the 1920s by the insertion of a copper joint to connect two pieces of shorter bamboo, which allows the length of the bamboo to be modified so that minute adjustment to its fundamental pitch can be made. The Xindi, "new flute", is a 1930s redesign of the Chinese flute incorporating western influences on the basis of equal temperament. In order to achieve a greater vibrancy and loudness with instruments (not to mention longevity), many string instruments are no longer strung with silk but with steel or nylon. For example, metal strings began to be used in place of the traditional silk ones in the 1950s for pipa, resulting in a change in the sound of the pipa which became brighter and stronger. Notation Before the 20th century Chinese used the gongche notation system, in modern times the Jianpu system is common. Western staff notation however is also used. Performance In common with the music traditions of other Asian cultures, such as Persia and India, one strand of traditional Chinese music consists of a repertoire of traditional melodies, together known as qupai, in which tempo and ornamentation vary according to the mood of the instrumentalist, the audience, and their reaction to what is being played, the same melody can be used to serve many different roles be it merry, melancholic or martial (this can be glimpsed in the love theme of the Butterfly Lovers' Violin Concerto where the same melody at different points in the lover's story reflects elation, turbulence and dejection). Many modern performers now play pieces by following a score in a standard way rather than in the changeable reflective individual way of tradition, this can at times lead to the feeling that a performance has been rushed. Modern popular music Pop music Chinese popular music found its beginnings in the shidaiqu genre. The shidaiqu genre was founded by Li Jinhui in mainland China and was influenced by Western jazz artists like Buck Clayton.