What is the connection between Jason and Marilyn Mason?

Unbeknownst to his girlfriend of over a year Heather Hart, Jason had a short affair with Marilyn Mason during their mentor/mentee relationship. Marilyn Mason had started out as Jason Taverner's protégée and he had secured her two singing auditions with major record labels while maintaining an active sex life with her. The two have not seen each other in six months upon the opening of the novel, however, so her call to him is a surprise.