It should be no surprise that Meryl Streep can sing. (The woman is capable of anything!) But before starring in the musical film adaptation of “Mamma Mia!,” Streep graced us with her voice in Mike Nichols’ 1990 “Postcards from the Edge,” alongside Shirley MacLaine. Streep didn’t sing again in a film until “Mamma Mia!” 18 years later.