Such occasions might be cited in great numbers. Not infrequently a negro who has assumed the position of song leader sings a line while the others join in with a chorus of singing and shouting. When the leader has given all the lines that he knows, he will often continue in the simplest manner possible, as if he had known them for a long time, to improvise lines, which often have little meaning, but which fit into the tune and sound well. This process may be continued indefinitely, sometimes with repetition of lines already uttered but slightly varied and the emphasis placed on the differing particular. It thus happens that the songs need not have a limit. The necessity of the occasion becomes the cause for the invention of the song. Itinerant worshippers are often thus gratified to sing to new congregations. As a rule the negroes always give attention and respect to strangers so that the man or woman who comes to them is at liberty to sing old or new songs, and they often become skilled in improvising songs. The new songs are then learned and begin their history as folk-song. Again, negroes often feel themselves called upon to introduce new features into some of their songs and conceive of various novelties. The negro's feeling toward leadership puts a premium upon such a practice. In this effort, a song that is little known among the negroes will be changed in some particulars, printed on a sheet of paper and distributed as the song of brother or sister So and So. The song may be found in a hymn book. However, songs entirely new and the efforts of their own poetic attempts are often thus circulated. This gives rise to a new class of negro spirituals, examples of which may be seen in the following pages.