The interval of the octave is material enough for a vocal exercise, one that sets the voice in good order and creates the “imposto,” the anchoring or positioning of the mechanism. The bottom note is reiterated fully on ah, or ah, ay, ee ,oh, oo, short quarters in common time, like the skipping of a rock, each note demands another. The octave above is sung as an echo of the lower, in the same rhythm and with twice the rhythmic élan, half volume or less, having the same position of the lower octave. If having trouble, softer, “like unto the spell of a magic echo.” Practice this until you make it your own, the sovereign octave, the exercise to which I return every day.