Mariachi was heavily involved in cultural promotion as a way to create a unified Mexican identity after the end of the Mexican Revolution. One of these efforts was the promotion of mariachi as an international symbol of Mexican identity, first with radio and sound recordings and later with films. Mexico built a nationwide radio broadcasting network in the 1920s such as XEB and XEW, which began broadcasting mariachi music as a media production, rather than as a music for social events. This music was already being modified in part due to the advent of sound recording. For example, most son jaliscense
Mariachi song due to voice qualities. Mariachi vocalization shows influences from a number of styles such as bolero (a romantic style), huapango (using falsetto), son jalisciense (an aggressive style) and more. Voices must be strong to be heard over amplified instruments. Vocal style emphasizes operatic qualities and instrumental performance demonstrates a level of virtuosity that reflects advanced musical training. Historically, mariachi groups have been made up of men but there is growing acceptance of female mariachis. As mariachi groups are expected to play requests, they may need to know hundreds of different songs. Most songs are about machismo, love, betrayal, death,