Interchange Third edition is a four-level series for adult and young-adult learners of English from the beginning to the high-intermediate level. The Class Audio Cassettes include the Conversations, Grammar Focus frames, listening activities, Pronunciation practice, and self-study section from the Student's Books, all recorded in natural conversational English. Also included are the listening sections of the Quizzes found in the Teacher's Edition. The Class Audio program is also available on audio CDs.