There may be some music whose composer deliberately tried to avoid any repetition at all. However, most music has a specific pattern of repetition. Mozart likes to repeat a phrase, only twice, and then go on. Czerny uses the repeat sign every eight measures or so. Bach repeats an air, or a tune, over and over with different chord structure underneath it. Beethoven, well, Beethoven repeats and adds onto the theme until he finally gets it to the majestic proportions he envisions. Popular music has verses, a bridge, and more verses. Older popular music merely has verses that repeat each other.