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
El Mariachi were simply condoms filled with fake blood and fixed over weightlifting belts. Rodriguez also noted the use of improvisation. The tortoise that crawls in front of the Mariachi was not planned, but was kept in as a good idea. Similarly, there is a scene in which the Mariachi buys a coconut, but Rodriguez forgot to show him paying for the fruit; instead of driving back to the place to shoot additional scenes, Rodriguez decided to build in a voice-over in which the Mariachi asserts that the coconuts were for free. Improvisation was also useful to cover up continuity mistakes: at