The Key of D, from the Armonía

D major harmonises to D – Em – F#m – G – A – Bm – C#°; D minor to Dm – E° – F – Gm – Am – Bb – C. A son in this key mostly alternates the tonic and the dominant; a ranchera adds the subdominant; a bolero reaches for the submediant and the supertonic on its way home.

Inside the armonía this instrument is the top of the armonía — five re-entrant strings whose open third is the highest open pitch on the instrument, so every strum lands as one tight treble block instead of a spread stack, and the shape below is not a voicing choice so much as a section instruction — the whole armonía strikes the same mánico in unison, on the same slot, or the chord stops being one event.

Learn the tonic, subdominant and dominant in D until the hand goes there unasked, and the repertoire in this key is largely playable before anybody names a form.