The register action of the organ of San Pedro Tidaá is unique in Oaxaca.  The row of drawknobs nearly at keyboard level and their connecting trundles were built horizontally rather than vertically. A modified reservoir/wedge bellows was installed inside the case which would have been operated by a lever from the open left side. This seems to have been the original design since the register action and the interior bellows were interdependent. The horizontal register draws left space inside the case for the bellows. This would not have been possible with normal vertical trundles. 

However, the neoclassical case decoration is standard for its time and includes denticles under the cornices, serrated leaf motifs decorating the upper case, and carved lambrequins (resembling an upside-down glove) on the lower case. Iron braces anchored to the wall sustained the organ in an upright position. However, it still leans forward, perhaps missing the weight of the side panels and the hips. In 2022, the IOHIO straightened, cleaned, and positioned the five largest pipes in the central tower in front of the five wooden pipes.