"He had to learn to sing, readily and accurately, all the tunes that were used in the many distinct Soma-sacrifices, and he had also to know which strophes were required for each sacrifice and in what order they were sung. Therefore, that the young priest might master all the tunes thoroughly and have any one at command at any moment, each was connected with a single stanza of the right metre, and the teacher made his pupils sing it over and over again, until tune and stanza were firmly imprinted, in indissoluble association, in the memory."