Music producer David Foster on “Boop!,” Barbra, and ballads

For the past fifty years, David Foster produced some of music’s most iconic artists, and won 16 Grammy Awards along the way. But the hit-maker’s latest project is the Tony-nominated “Boop! The Musical,” for which Foster wrote about fifty songs. He talks with correspondent Tracy Smith about discovering such unique talents as Celine Dion and Michael Bublé; working with such demanding artists as Barbra Streisand and the rock group Chicago; and what he really thinks about legacy.