from www.loc.gov:
The corrido is a type of socially relevant narrative ballad that served in Mexico as the main informational and educational outlet.
Rancheras, literally “music of the ranches,” are traditional songs usually accompanied by guitar and/or horns.
The merging of European and indigenous Mexican musical traditions has long been a hallmark of Mexican American music beyond the church. Corridos gave rise to other forms of music such as Tejano (literally “Texas music”). Tejano music, the name given to several different forms of folk music developed by the Mexican American community in Texas, combines the waltz and polka stylings brought to Texas in the mid-nineteenth century by northern European immigrants with Spanish-language songs that originated south of the border and were passed down through generations of Mexicans.
Habanera music is also found among Mexican Americans. It has a meter influenced by the music of North Africa and is found throughout the Spanish speaking world today.
Conjunto music is one of the dominant dance music forms of Mexican Americans today. Related to Tejano music, its roots lie in South Texas at the end of the nineteenth Century, following the introduction of the button accordion into Mexican working-class communities along the Texas-Mexican border by Northern European immigrants. The accordion-based musical form was used to accompany celebrations of all kinds. Thanks to a strong recording history from the 1920s onwards, conjunto grew to become the most powerful musical symbol of Mexican American working-class culture.
Mariachi music is perhaps the most well-known Mexican American folk music form, having gained wide popularity throughout the United States in the latter half of the twentieth century mostly through its promotion in school bands and at mariachi festivals.
Mariachi originated in rural Mexico in the nineteenth century and, like Tejano, was eventually influenced by the polka and waltz. The typical mariachi ensemble consists of violins, accordions, trumpets and guitars. Mexican folk harps are also sometimes employed. There is generally no lead singer. All players sing choruses and take turns singing the lead. Mariachi vocalization, which emphasizes an operative quality, encompasses a romantic “bolero” sound, falsetto singing, and a more aggressive style known as son jaliscense.
Son Jarocho is another well-known Mexican music style that has gained popularity in the United States. Fusing Spanish and African elements, much of it is syncopated, combines instrumental music with improvised and fixed oral poetry along romantic or bawdy themes, and is sung in a call-and-response format. The instrumentation usually includes a large diatonic harp (arpa), a small, eight-stringed guitar (jarana) and a four-stringed guitar (requinto).