MasterClass is an online education platform where people buy a subscription and gain access to tutorials and lectures.
It is all pre-recorded by excerpts in various fields.
Mariah Carey now has her  own MasterClass series.
It is available to watch now and includes nine different lessons and a guide you can download that features exclusive content.
The course is titled, Mariah Carey Teaches the Voice as an Instrument.
Lessons include:
Writing With Samples
Producing Your Voice
Taking Care of Your Voice
Surviving in the Music Industry
Lyricism: Write About the Realness

And she teaches about background vocals.