Throughout Mexico (and for that matter, America), huge professional billboards advertise products and services from large, national or international corporations. Conversely, bardas are used mainly for advertising local concerts and dances, as well as political and social campaigns for health and education, all aimed at the lowest-income population. Bardas constitute a cheap and immediate form of marketing ($2 per foot as compared to $42 for a billboard) that speaks through scale, repetition, bright colors, and type communicating catchy slogans or the Americanized names of popular bands. And there are no restrictions on what they say or look like.

"The sign painters or rotulistas never get special permits or pay any rent for the walls they paint on," Cué said. "The authorities tolerate and turn a blind eye to these signs when they are painted on public property such as underpasses, cemetery walls, and roadsides due to the social value of the events that they advertise and to the tradition behind these painted walls as part of Mexico's visual culture." In fact, she added, in this country known for political corruption, "Many of the rotulistas benefit from the protection of politicians for whom they paint political campaign walls." When private property is involved, sign painters pay the home owners with free dance tickets: "People prefer to have the local dance advertised on their outside wall than graffiti or simple decay."

The design "formula" for these signs was the same in all 12 states in central Mexico that Cué visited for her research. For rorulistas, she learned that creative authorship is not important. Their goal is produce works that looks like everybody else's so that it can be directly linked to a particular type of music event. "It is a type of vernacular branding," Cué writes in the book. "More than originality, craft and speed are most important." Change did occur in 1980s when a new style emerged for the Sonideros or DJs. Dimension and symmetry become newly important elements of the type arrangements, and visual effects such as metal and sparks -- in the style of heavy-metal band trademarks - started showing up.

"Today, the innovators are the children from the older generation of rotulistas or masters who often have very hard-earned degrees in graphic arts, graphic design, or even architecture," she said. In fact, these days rotulistas are likely to make a modest living "if they have a territory with enough walls that is, informally, theirs. They also need a van or pick-up truck to transport themselves and their equipment (paint, air compressor, and lyme) swiftly from one wall to the next, and a politician, impresario, or community leader who gives them work constantly." Most barda painters, though, have other jobs working as factory workers, car mechanics, farmers, or even in their own bands. What's more, there is frequent turnover. Bardas are usually painted two weeks before an event. For that period, other painters don't cover over the message; afterward those spaces are free to use.