This article: The one-act opera genre had become increasingly popular in Italy following the 1890 competition sponsored by publisher Edoardo Sonzogno for the best such work, which was won by the young Pietro Mascagni's Cavalleria rusticana. With Tosca essentially completed by November 1899, Puccini sought a new project. Among sources he considered, before proceeding with Madama Butterfly, were three works by French dramatist Alphonse Daudet that Puccini thought might be made into a trilogy of one-act operas.After Butterfly premiered in 1904, Puccini again had difficulty finding a new subject. He further considered the idea of composing three one-act operas to be performed together, but found his publisher, Giulio Ricordi, firmly opposed to such a project, convinced that it would be expensive to cast and produce. The composer then planned to work with his longtime librettist, Giuseppe Giacosa, on an opera about Marie Antoinette, a project frustrated by the librettist's illness. Puccini wrote in November 1905, "Will we go back to it? [Maria Antonietta] If I find three one-act works that suit me, I'll put off M.A."  Puccini pursued neither project, as Giacosa's illness led to his death in September 1906.In March 1907, Puccini wrote to Carlo Clausetti, Ricordi's representative in Naples, proposing three one-act operas based on scenes from stories by Russian novelist Maxim Gorky. By May the composer had set aside this proposal to concentrate on the project which became La fanciulla del West, although he did not wholly abandon the idea of a multiple-opera evening. His next idea in this vein, some years later, was for a two-opera bill, one tragic and one comic; he later expanded this to include a third opera with a mystic or religious tone. By November 1916 Puccini had completed the "tragic" element, which became Il tabarro, but he still lacked ideas for the other two works. He considered staging Il tabarro in combination with his own early work Le Villi, or with other two-act operas which might be used to round out the evening's... contains an answer for the question: Who later expanded their original idea to include a third opera with mystic or religious tones?, what is it ?
Answer:
Puccini