After his polemics with the Czech critics during the 1920s, Martinů's career transformed a number of times. The more he prolonged his residence in Paris, the more he became torn over the timing of his return. Early in the 1930s he declined an offer to teach at the Brno Conservatory, and with his sights set on Prague, a second, more emphatic offer could not lure him to the Moravian capital. A stylistic shift occurs in his music at this time. As the elements of jazz, pastiche, and imitation disappear, he began to balance the rhythmic dynamism of his previous years with polyphony in a more purely neoclassical style; the milestone work in this transition was his Piano Trio no. 1, Five Short Pieces (1930). For larger ensembles, the concertante techniques of the eighteenth-century concerto grosso became his new point of departure: crowning achievements in this style took form in his Concerto Grosso (1937), Tre ricercari (1938), and Double Concerto for Two String Orchestras, Piano, and Timpani (1938).

Forming an independent stream to his instrumental works was an ambitious project for the Czech theater. Here he continued his polemics with the Czech critics, insisting that national opera was still appraised too much according to Wagnerian aesthetics. For Martinů, disentangling the Gesamtkunstwerk meant working with the various parameters of the music and stage individually rather than dictating sentiment by unifying forces; that viewers gain greater freedom in interpreting the work on their own was key to his ideal. In his “singing-ballet” Špalíček (1932), for example, where he employed the folklore captured in albums from Counterreformation Bohemia, he worked without a central narrative, allowing the scenes to unfold in continuous fluctuation. And in The Plays of Mary (1934), an operatic cycle of medieval miracle stories, he decentralized the narrative by circulating it through the main characters, dancers, choral numbers, and spoken narration. His moral victory on the domestic scene was the production of his surrealist opera Julietta, or the Key to Dreams (1937) at the Prague National Theater under Talich in 1938, which received great critical acclaim. However, vocal opposition to this work came from the Nejedlý School, which was beginning to take Martinů much more seriously and laid out extensive grounds against his theatrical project in general.