Listening to songs is an essential part of language learning. Types of songs will vary according to stage of learning.
One of the essential things in the first stages of teaching/learning a new language is to make the learner aware of tone, stress intonation, etc., anything that will help put into place good oral communication skills. Children songs are perfect for that matter. They usually consist of simple spoken sounds (mind I'm not writing "words" at that stage), that will be easily picked and repeated by the budding learner who will be able to learn them by heart and sing them, thus imprinting in his mind rhythm and sounds. I include traditional nursery rhymes and tongue twisters in children songs, which are part of a language cultural element and culture is essential in the learning of a language.
In later stages, when the learner has more more vocabulary and grasp of the language, other types of songs will be more appropriate so that the meaning of words in sentences can become part of the learning process.