Pitch Drift in a cappella choral singing > FutureLearn is a great idea and it's free!
I have recently started a FutureLearn course on "Critical Listening for Studio Production" presented by Queens University, Belfast. It consists of 7 weekly blocks each taking around 3 hours (although you can take as long as you wish). There is some theory and simply hundreds of listening tests with a small but tricky assessment at the end of each week. Why not visit the FutureLearn website (www.futurelearn.com) and book yourself a place on one of the many free courses offered. By the way a MOOC is a Massive Open Online Course - obviously!