The audio lectures from the videos. These are the lectures Chap gives his students every year. Over 9 hours of teaching! Each lecture is from 18-30 minutes. If put on CDs, it would require numerous CDs and an exorbitant cost! Instead, these MP3s are on a DVD-ROM for you to load to your smart phone or music player. You get 24 lectures for less than the price of an itunes song each! For more information visit this page.