Son huasteco is the folk trio tradition of the Huasteca region (spanning San Luis Potosí, Hidalgo, Veracruz, and Tamaulipas states in northeastern Mexico). The instrumentation is fixed at three: a single violin carrying the melody, the small jarana huasteca (a five-string chord-guitar), and the larger quinta huapanguera (a five-string bass-guitar). The son huasteco distinguishing feature is not the instrumentation but the vocal exchange: two male singers alternate, one in normal register and one in falsetto, trading lines and improvising back at each other. Songs run 6/8 against 3/4 hemiola, 120–160 BPM, with dancers stamping the tarima (wooden platform) as part of the rhythm section.

Son huasteco crystallised in the eighteenth and nineteenth centuries as European colonial dance music (fandango, bolero, waltz), local Huastec indigenous poetic tradition, and Afro-mestizo percussion sense fused. It sits sibling to son jarocho of coastal Veracruz and to son of Guerrero. What sets it apart is the single-violin melodic centre; the two guitars stay in accompaniment. Lyrics use the ten-syllable décima line, and the singers improvise verses on the spot in a tradition called trova. The mid-twentieth century produced professional touring trios; the 1955 formation of Trio Los Camperos de Valles started a nearly-seven-decade run that continues today.

The falsetto exchange is the immediate point of entry. One singer takes the verse in chest voice, the other responds in falsetto, then flips it. Called alternancia, this response format defines son huasteco. The violin plays the same melodic phrase repeatedly with different ornamentation each time. Trio Los Camperos de Valles's 'La Petenera' shows all elements at once.

Trio Los Camperos de Valles, 'La Petenera.' Their 2000s live recordings for the actual fandango-atmosphere. Late night, quiet room, moderate speaker volume — this is folk music that lasts for hours in its native context, and the recorded version should be listened to as an atmospheric sample of that.

The name Huasteco derives from the Huastec indigenous people whose language was Teotl-family adjacent to Nahuatl. The modern son huasteco is mestizo (mixed-heritage) in musical origin, but the regional name preserves the indigenous root. Violin tuning is standard Western G-D-A-E, but son huasteco violinists routinely finger between-string positions considered incorrect in classical training — likely preserving older folk technique. Trio Los Camperos de Valles performed at the Kennedy Center in Washington in 2018.