The Key of A, from the Armonía

A major harmonises to A – Bm – C#m – D – E – F#m – G#°; A minor to Am – B° – C – Dm – Em – F – G. 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 A until the hand goes there unasked, and the repertoire in this key is largely playable before anybody names a form.