The organ of San Juan Ihualtepec, along with those in Ahuehuetitlan, Tamazola, and Zapotitlan, are located in relatively close communities in the flat northwestern region of the Mixteca Baja near the border with the state of Puebla.  They were built by the Castro family organbuilding company in Puebla, which dominated organ building in this area throughout the 19th century. Castro organs were well made and elegant in appearance, yet immediately distinguishable from Oaxaca organs. Their distinctive features include the straight sides of the case (without hips), square or rectangular panels rather than carved decoration on the lower case, symmetrical perforations or lattice grids on the sides and back, a curved upper profile above the interior towers, stop knobs in two rows, an extended keyboard, and metal wind conduits. The stop names are typical of Puebla, but not Oaxaca, organ building. The Ihualtepec organ is the first in Oaxaca to be signed by a Castro organbuilder. It is a slightly smaller version of the Ahuehuetitlán organ and does not have reeds or an 8´ tonal base (bardón).