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

F Phrygian 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 F marked, so home stays visible from anywhere in the pattern.

Very dark minor with a half-step above the tonic. Spanish, Flamenco, and metal flavor — exotic, tense, and mysterious.

Heard in: Flamenco, metal, dark film scores — Carlos Santana solos, Joe Satriani's "War", Moorish and Andalusian music.

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.