Named for its northern Mexican birthplace, Norteño (or, more formally, "la musica norteña") is a small-group dance music driven by accordion and bajo sexto. In Texas, norteño music is generally referred to as conjunto (after the ensemble that performs it), with the only real differences being location (and corresponding changes in accent), and the preference of norteño for the more traditional corrido song form over the ranchera; norteño is also very similar to Tejano music, except that its sensibility is more rural and traditional than modern or urban, and its rhythmic drive is somewhat less pronounced. In addition to being primarily dance-oriented, norteño has also had a historical role as the music of the working classes, its celebratory exuberance and often tough, rowdy lyrical themes setting it apart. The standard ensemble features an accordion (usually a simple diatonic model), bajo sexto (a baritone-range twelve-string guitar), bass, and drums, along with one or two expressive vocalists. This format solidified around the 1950s, but its roots date back to the late 1800s, when the Mexican population in the area was introduced to the accordion and to various European folk dances -- polkas, waltzes, redovas, mazurkas, schottisches -- by German and Czech immigrants living in southern Texas. Eventually, Mexican musical forms like huapango and cancion ranchera were fused with the European dance rhythms, producing a unique hybrid. The bajo sexto evolved into an important accompaniment for the accordion, especially when accordionist Narciso Martinez discovered in the 1930s that his partner, bajo sexto player Santiago Almeida, could play all of the accordion's bass parts; this freed Martinez to concentrate on virtuosic, upper-register melodic runs, and produced a lighter, cleaner interaction between the two. Santiago Jimenez introduced string bass in 1936, and Valerio Longoria began utilizing trap drums as percussive accompaniment in 1949 (although for a time they were considered too noisy for recording sessions); Longoria also began adding vocals, transforming what had previously been an entirely instrumental music. Norteño's popularity exploded in the 1950s, as the border-area population became more urbanized and reached out for familiar comforts in their new surroundings; as the music spread into larger dance halls, electric instruments and amplification followed. Although norteño could encompass a variety of song forms and rhythms, its dominant mode of expression was a corrido (story-song) performed over a polka or waltz rhythm. During the 1960s, the virtuosic explorations of el Conjunto Bernal pushed the music's technical demands to new heights, and by the following decade, norteño/conjunto was solidly entrenched as the most popular style of music among the Mexican working classes in Texas and northern Mexico. At that point, norteño's formal development essentially halted, although performers like Flaco Jimenez flirted with pop accessibility, and others introduced synthesizers to the sound during the 1980s. Thanks to groups like Los Bravos del Norte and Los Tigres del Norte, norteño's popularity only continued at the beginning of the new millennium, attracting tremendous attention from Latinos all over America and other parts of Mexico, as well as fans in Europe and Japan.