Function assemble_all_lyrics 

pub fn assemble_all_lyrics(
    stream: &Stream,
    max_lyrics: IntegerType,
    lyric_separation: &str,
    word_separator: &str,
) -> String

Every line of a stream’s lyrics, each assembled by assemble_lyrics, one after another with lyric_separation before each but the first: music21’s assembleAllLyrics. Lines one to max_lyrics - 1 are read, as music21 reads them, and a line with no lyrics at all is left out, though a separator still comes before each line after the first.