How we learned songs in music class when I was in grade school, in California: We didn't have books; the songs were on phonograph records, which were badly worn (this was in the days of 78s) & almost unintelligible. The teacher would play a record, and you would raise your hand if you thought you could guess some of the words, and if you were right, she would write them on the blackboard. She would play it over until the class had deciphered the whole song. By that time, we had heard the tune so many times that we knew it, and the words were in front of us, so we could all sing it.

Perhaps, in our day, the process could be computerized. %^)