Some of the advantages of using a cassette recorder are:
First, it gives the students the chance to listen to a variety of voices apart from the teacher’s, and it brings native speakers’ voices into the classroom.
Second, recorded material is useful for listening to dialogues, interviews, discussions, etc. where there is more than one person speaking at the same time. Otherwise the teacher has to act the part of more than one person.
Third, it is very useful for intensive listening, because the cassette can be stopped and a phrase played over and over again. This kind of listening is called intensive listening.