You’ve probably done the math by now and concluded that Fiddler premiered in 1964, toward the end of what many scholars refer to as Broadway’s “Golden Age.” Most commentators place the beginning of that period with Oklahoma!, which also happens to be receiving a revival in Austin this summer, courtesy of Zilker Theatre Productions. But that’s not all, folks: At least 11 – count ‘em, 11 – musicals are running on area stages during August. That’s an average of one opening every three days.