A Mixolydian — Puerto Rican Cuatro (Antiguo A-D-G-C-F)

A Mixolydian is 7 notes to the octave (modes family), drawn here across the Puerto Rican Cuatro (Antiguo A-D-G-C-F)'s A-D-G-C-F strings with every A marked, so home stays visible from anywhere in the pattern.

Major with a flatted 7th (b7) — bright and bluesy. The dominant chord turned into a tonal center with a rock/folk edge.

Heard in: "Sweet Home Chicago", "Norwegian Wood" (Beatles), Celtic and folk music — anywhere a major sound needs a darker, looser edge.

Five courses spanning a minor thirteenth give a scale room to breathe: three or four notes to a course in first position, and a top string clear enough that a melody can live there while the rest of the grip stays down. These maps light every root so a run knows where home is before it leaves.

Work it in one position before you work it up the neck. The doubled courses forgive nothing: a fret held half a millimetre short buzzes on one string of the pair and rings on the other, and that difference is audible long before the run is fast.