Cantonese opera pieces are classified either as "theatrical" or "singing stage" (歌坛). The theatrical style of music is further classified into western music (西乐) and Chinese music (中乐). While the "singing stage" style is always Western music, the theatrical style can be Chinese or western music. The "four great male vocals" (四大平喉) were notable exponents of the "single stage" style in the early 20th century.
The western music in Cantonese opera is accompanied by strings, woodwinds, brass plus electrified instruments. Lyrics are written to fit the play's melodies, although one song can contain multiple melodies, performers being able to add their own elements. Whether a song is well performed depends on the performers' own emotional involvement and ability.
Cantonese instrumental music was called ching yam prior to the establishment of the People's Republic in 1949. Cantonese instrumental tunes have been used in Cantonese opera, either as incidental instrumental music or as fixed tunes to which new texts were composed, since the 1930s.
The use of instruments in Cantonese opera is influenced by both western and eastern cultures. The reason for this is that Canton (Guangzhou) was one of the earliest places in China to establish trade relationships with the western civilizations. In addition, Hong Kong was under heavy western influence when it was a British colony. These factors contributed to the observed western elements in Cantonese opera.
For instance, the use of erhu (two string bowed fiddle), saxophones, guitars and the congas have demonstrated how diversified the musical instruments in Cantonese operas are.