Sometime when I was around nine years old, my music teacher brought in an audio-visual aid into our classroom and showed us a half-hour film documentary about what made up a mariachi band. I=The narrator introduced several members of the band and what they played. He demonstrated things like how the strings and brass often complemented each other on melodies and harmonies, while the guitar and vihuela often provided the rhythm and accompaniment, and how the guitarron provided the bass foundation, while the vocalists simply sang when the brass and string sections were at rest.
Somewhere in the middle of that presentation, I heard the guy who was one of the guitar players say how he strummed a G-chord at an eighth-note pace, at a quarter note BPM of 100. He said something like how there was a slight delay between the first guitar player playing those eighth notes and the other one, so that it would sound something like this:
Since this technique is present throughout the whole piece, I did not include time, sufficient to say that starting about ten seconds, the guitars really start to pick up speed. The idea was for it to sound like sixteenth notes, so when I was a little older, I tried doing that on a guitar by rapidly strumming up and down at that pace, but it was difficult to do. If I knew where that documentary was, I could go back and listen to it, but unfortunately I don't know what it's called.
If anyone here has mariachi experience and can provide me with a better explanation of what was going on, I would really appreciate it.