Horse Opera Meaning

Example : 1952, "Way Out West," Time, 3 Nov.:  Three new examples of Hollywood's staple commodity, the horse opera, all filmed in color, contain the full quota of galloping and gunplay.1856, "Affairs in California: San Francisco," New York Times, 31 Mar. (retrieved 30 Mar. 2009):  The Ravels, after having played a successful engagement at the Metropolitan, closed last evening, and sail to-day for New-Orleans, and now we have no amusement but nigger minstrels and the horse opera—i.e., circus.1879, "On the Parisian Boards: Another of Jules Verne's Stories on the Stage," New York Times, 29 Jan. (retrieved 30 Mar. 2009):  Nor is it much easier to give the analysis of this extraordinary odyssey, which relates the trials, sufferings, and adventures of an ex-Sous-Prefêt, who has married a circus rider, and has abandoned home, friends, and position, to become the manager of an itinerant horse-opera.