One opera in the 1973 crop, Transformations by Conrad Susa, paid homage to the usually missing element by incorporating a variety of pop styles, and won respect for its sophisticated embodiment of the poems by Anne Sexton that serve as its libretto. If our arbitrary benchmark for showing “success” had been two decades instead of one, Transformations would have made it onto the list. But just barely; it has not become a repertory piece, and unlike “Tie a Yellow Ribbon,” it has not evaded the accusation of “pastiche.” The tunes make something like the effect of a versatile actor imitating multiple voices. The same problem has encumbered the path of several essays by William Bolcom, who can give an expert demo sample of any idiom. Once you’ve made a point of showing the ability to be a clever impostor, you have to expect a certain wariness before people trust that you’re being anything else.

However, what other impression could he give? It was fine for Mozart to be “derivative” with respect to Gluck and Haydn; Verdi imitated Donizetti as baldly as Donizetti had imitated Rossini; but from what or whom might a 21st-century opera-wright “derive” a melodic idiom? From Turandot? From plainchant? Sondheim? Taylor Swift? Participants in an ongoing tradition don’t have to make a conscious choice; standing outside the flow and trying to rejoin it may be like trying to mount a cantering horse.

Or maybe not. It is easy to say something is unlikely to be done until someone does it. Wagner seemed for a while to have paralyzed German opera (Liszt, Brahms, Bruckner, Mahler all shied away from theater composition; Richard Strauss didn’t find his stage legs until around the age of forty). One could have said, and some did, that Wagner’s radical achievements pointed no path forward. But then his one-time assistant Engelbert Humperdinck produced a textbook exposition of Wagnerian techniques and, with it, the most popular new German opera in a generation (Hänsel und Gretel, premiered a decade after the Master’s death, is one of those that met our benchmarks for “success” many times over, and within three or four years, not ten). Soon after came Puccini, the real heir of Wagner in musical terms though different as could be in dramatic purposes, who remains to this day the most-performed opera composer of all.

Puccini and Humperdinck had absorbed Wagner’s method of generating symphonic flow from a prevailingly contrapuntal texture employing discrete motives, and they were able to master this in technical detail while writing inspired music in their own voices. Anybody can set down a sequence of motives and tick off spots in the libretto where their return would be apt; the trick is composing a coherent, beautiful, compelling score out of them. Music that music-lovers can love. The “crisis” of how to proceed after Wagner evaporated, not because of any particular line of thinking but because some composers stepped up and did the deed. Everything I’ve said about the dilemmas of 21st-century opera-making is just four or five solid successes away from being revealed as needless worry.