The zarzuela is usually a one-act piece (although sometimes it is permitted to run into two or more acts) in which the music is freely interrupted by spoken dialogue, and that in turn gives way to national dances. Very often the entire score is danced as well as sung. The subject is usually comic and often topical, although it may be serious, poetic, or even tragic. The actors often introduce dialogue of their own, "gagging" freely; sometimes they engage in long impromptu conversations with members of the audience. They also embroider on the music after the fashion of the great singers of the old Italian opera (Dr. de Lafontaine asserts that Spanish audiences, even in cabarets, demand embroidery of this sort). The music is spirited and lively, and in the dances, Andalusian, _flamenco_, or Sevillan, as the case may be, it attains its best results. H. V. Hamilton, in his essay on the subject in Grove's Dictionary, says, "The music is ... apt to be vague in form when the national dance and folk-song forms are avoided. The orchestration is a little blatant." It will be seen that this description suits Granados's _Goyescas_ (the opera), which is on its safest ground during the dances and becomes excessively vague at other times; but _Goyescas_ is not a zarzuela, because there is no spoken dialogue. Otherwise it bears the earmarks. A zarzuela stands somewhere between a French _revue_ and opéra-comique. It is usually, however, more informal in tone than the latter and often decidedly more serious than the former. All the musicians in Spain since the form was invented (excepting, of course, certain exclusively religious composers), and most of the poets and playwrights, have contributed numerous examples. Thus Calderon wrote the first zarzuela, and Lope de Vega contributed words to entertainments much in the same order. In our day Miguel Echegaray, brother of José Echegaray, has written one of the most popular zarzuelas, _Gigantes y Cabezudos_ (the music by Caballero). The subject is the fiesta of Santa María del Pilar. It has had many a long run and is often revived. Another very popular zarzuela, which was almost, if not quite, heard in New York, is _La Gran Vía_ (by Valverde, _père_), which has been performed in London in extended form. The principal theatres for the zarzuela in Madrid are (or were until recently) that of the Calle de Jovellanos, called the Teatro de Zarzuela, and the Apolo. Usually four separate zarzuelas are performed in one evening before as many audiences.