Metodo pratico
Published first in London in 1834, Nicolo Vaccaj's Metodo pratico di canto italiano per camera diviso in 15 lezioni (A practical method of Italian chamber singing, divided into 15 lessons) is the most popular vocal method in the world. To date, it has been published in over 40 editions.
The meaning of the Italian word metodo is "a way." Vaccaj apparently wanted to introduce an organized approach to learning to sing.
He divided his method into 15 lessons or 15 exercises with a total of 22 songs.