Keys, Diatonically — Guitar
Pick a key. Its diatonic chords, and this instrument's job across them.
Mariachi harmony is plainer than the ensemble sounds: a son largely alternates the tonic and the dominant, a ranchera adds the subdominant, and the slow numbers are where the submediant and the supertonic earn their place. Naming the function is enough — no number is needed to call one.
Pick a key below and it arrives as its diatonic chords, with what this instrument does as the harmony moves under a called form.