A folksong is shorter than a ballad but are aimed at a more mature audience than nursery rhymes. They have been sung for many generations and were made up by unknown singers and then verses were added by other singers. They appeal to children because the lyrics are often colorful and their melodies are catchy but accessible. Folksongs can be sung easily a capella (without instrumental accompaniment). Many folksongs have been made into children's books. Examples are: