During the Southern Song period, Guangzhou became the cultural center of the region. Cantonese emerged as the prestige variety of Yue Chinese when the port city of Guangzhou on the Pearl River Delta became the largest port in China, with a trade network stretching as far as Arabia. Cantonese was also used in the popular "Yuè'ōu", "Mùyú" and "Nányīn" folksong genres, as well as Cantonese opera. Additionally, a distinct classical literature was developed in Cantonese, with Middle Chinese texts sounding more similar to modern Cantonese than other present-day Chinese varieties, including Mandarin.