Special Feature: Billboard a la Musica Mexicana -- Speaking Out

While regional Mexican is the top-selling genre of Latin music in the United States, according to Nielsen SoundScan, it's also the one most affected by non-musical forces.

The economy, immigration and even the loss of physical retailers have all disproportionately affected sales of the music and the robustness of the genre in general.

But by the same token, this genre is full of heroes -- artists who have stepped up to defend causes and people, through both their music and actions.