In the adjoining courtyard to Union Station, a union rally - the AFSCME (American Federation of State, County and Municipal Employees), Local 1902/1001. These folks run the water system here, and they want a new contract.  Be that as it may, for this rally they hired a mariachi band - the best I've ever heard.  Photos from Tuesday, August 16, 2005.

From Mexican Mariachi Music and Instruments -

The mariachi ensemble and mariachi music originated in the Jalisco region and surrounding states of western Mexico, especially the city of Guadalajara.  A traditional mariachi included primarily string instruments, such as guitars; a large bass guitar called a guitarrón; a folk harp with 28–40 strings; violins; a flat-backed, five-string guitar; and vihuelas (guitars with round backs). In the Zacatecas and Los Altos regions of Mexico, a bass drum or snare drum was sometimes added to the group. Before cars, mariachi bands traveled from town to town by walking or by train, mule, or horse.

… The first large-scale mariachi festival in the United States occurred in San Antonio in 1979.  Linda Ronstadt, a pop music star who is a native of Tucson, Arizona, helped popularize mariachi music with a national tour and recording entitled "Canciones de Mi Padre."

More notes here - including why they're dressed this way.

Part of an extensive explanation, a bit on language here -

The word mariachi was long considered to be derived from marriage, the French word for marriage, since mariachi music is often played at weddings, but this theory has recently been discredited.  The earliest known appearance of the word mariachi in reference to music is from 1852, nearly ten years prior to the French intervention in 1861.  Another theory states that the word originated in the language of the Coca Indians in the early 16th century and originally referred to the wooden platform on which the musicians often performed, which was made of the wood of the Pilla or Cirimo tree.  Yet another theory claims that the guitars were made of this wood.

The band –