García's Method of Voice Placement

The stroke of the glottis is produced by means of a sudden opening of the glottis.

The air is first inhaled, and retired for a moment below the vocal cords, when the air, acting upon them abruptly, they suddenly open, producing a sound termed the stroke of the glottis. It is made upon precisely the same principle that a sound is produced when the air, having been located between the cheeks, the lips suddenly open for the pronunciation of the work pur. Persons having the habit of singing out of tune, often eradicate the fault by careful practice of the stroke of the glottis. The muscles controlling the vocal cords, however, may not a once obey the will. The brain often conceives the pitch of a tone, but the muscles controlling the vocal cords do not obey the dictates of the mind; hence the cords vary in tension, giving out tones of a varying pitch. When one sings out of tune from this cause, the difficulty can generally be entirely remedied, but when from a defective nerve organization relative to the hearing, it is impossible to fully eradicate it. There are those who can discern the slightest discord, but cannot sing the scale correctly; this proceeds from a physical laryngeal imperfection, or weakness, but as stated, can generally be cured; but when a person cannot notice any difference between high of low tone, the case may be considered almost hopeless. The practice of the study of the stroke of the glottis, should be carefully pursued by all persons intending to become singers, as it at once places the tones, thus preventing any possible change in the pitch, or quality of the voice; and the muscles are thus educated to instantly obey the will, and the requisite tension of the cords is gained for the pitch of the tone desired.

—Wheeler, Harry J. Vocal Physiology, Vocal Culture and Singing (1883): 44-45.

Harry J. Wheeler was a student of Manuel García and Francesco Lamperti. Find this text on the download page.