Bel Canto Resurgence

The Metropolitan Opera Guild presents a four part series on Bel Canto, drawing attention to its roots in the 1800's and including its resurgence in the 1950's by way of Maria Callas.
What is Bel Canto-a style or a solid vocal technique, or both? Who were its proponents then and why the resurgence? Who are the masters of it now?
Dates are Tuesdays at the Metropolitan Opera Guild:
May 21,  2:00-3:30 pm
May 28,  2:00-3:30 pm
June 04,  2:00-3:30 pm
June 08,  2:00-3:30 pm