Counted in three, and the first thing to notice is what the armonía is NOT doing: it is not playing the oom. That belongs to the guitarrón, which lands its root on the downbeat, and a strummed chord on top of it would only blur the one note the whole ensemble is tuned to hear as the harmony.
So slot 1 is a braked slap. The hand marks the beat, contributes weight, and adds no pitch on top of the bass note. The ringing chords answer on the second and third beats — the two pahs — and the bar has a declared rest in it so the slap is heard as a stop rather than as the start of a roll.
This is the cell most often written down wrong. A transcription that puts a down-stroke on every beat of the waltz is describing a guitar part, not an armonía part, and it doubles the bass into mud the moment a real guitarrón is standing next to it. The declared slap is the difference, and it is why the slot vocabulary treats a mute as a first-class value rather than as an accent mark on a stroke.
The same songs turn up counted in two, and the section does something quite different with them — see the polka-feel cell for the comparison. Nothing about the harmony changes; everything about where the weight falls does.
THE DECLARED REST IS DOING WORK. Slot 2 is written as a rest rather than left blank because a blank is ambiguous: it could mean the hand is resting or that whoever wrote the pattern down did not think about it. Declared, it says the hand comes off the strings and stays off for that slot, which is what makes the opening slap read as a stop rather than as the first stroke of a roll. Half of what this engine records is where the hand is NOT.
UNISON IS THE STANDARD, not an aspiration. The vihuela and the guitar play this identical sequence at the identical instant, an octave apart. The upper instrument gives the section its attack and the lower one gives it body, and neither is doing anything the other is not — which is why a waltz-feel ranchera falls apart the moment two players disagree about whether slot 2 is silent.
What the bar looks like from underneath is set out on the bass reference: the guitarrón has already claimed the downbeat, usually doubled at the octave, and everything this cell does is arranged around not covering it.