The outbreak of the war led to an extensive hiatus in Joan Manén's career, spanning five years where his international presence was interrupted. Manén decided to settle in Barcelona, ??to get involved in the city's musical environment and to develop a national career. During 1915 he made an extensive concert tour of Spain and Portugal accompanied by the pianist Fernando Ardèvol, performing works such as the César Franck's Sonata, a Beethoven Sonata, Bruch's Scottish Fantasy, and Lalo's Spanish Symphony. In November a historical recital took place at the Madrid Philharmonic Society: Manén performed the entire cycle of Beethoven's ten sonatas for violin and piano in three days with Enrique Granados at the piano, just weeks before Granados travelled to New York for the premiere of his opera “Goyescas”. Contemporary reviews stated that "both artists demonstrate interpretive criteria that deserves all our greatest and warmest praise. They put aside the artistic specialty that has made them famous and appear as devoted and surrendered servants before the Beethovenian altar. We do not know what applaud more, whether the refined and admirably serene style or the character without frights or violence. " (Hispano-American Musical Magazine, January 1916)
In November, 1916 Manén played the Beethoven sonata cycle again in Valencia, this time with the collaboration of the pianist Joaquín Nin. In July and November of the same year, Manén also made the first ever recording of the Beethoven and Mendelssohn Concerti for violin and orchestra, with the conductor Concordi Gelabert, for the record company “His Master’s Voice”.
On the 14th of March, 1917, during the seventh Catalan Music Festival at “Palau de la Músic”a in Barcelona, ??the choral work Els dos camins by Joan Manén was awarded the "Premi de la flor natural". Dedicated to the Orfeó Català and based on a popular melody, Manén’s piece was of great scope and vocal demand that transcended the original theme, with a poetic expressiveness emanating from the symbiosis between text and music. On the 21th of June, the pianist Guillermo Garganta and members of the “Quartet Renaixement” performed the Manén Quartet with piano Mobilis in Mobili at “Palau de la Música”.
Manén’s concert activity was considerably reduced in favour of composing for the entire year of 1917. It should be remembered that since before the war Manén had been working on a transcription series of short works by Baroque authors (Bach, Daquin, Gluck, Martini, Blas Laserna, Paradies ...) that he regularly included in his recitals. He also made new arrangements of sonatas by Tartini, Porpora and Nardini as well as of works by Paganini and Sarasate. In February, 1918, the Manén Festival was celebrated at “Palau de la Música”: three concerts with numerous symphonic works by Manén, as well as works by other authors. The composer organised these concerts himself in collaboration with the “Orfeó Català” in order to publicize his symphonic oeuvre since, although Manén was widely recognized as a violinist, a large part of the Barcelonian public was unaware of his compositional work and in particular of the symphonic production that had recently been programmed abroad. Among the works by Manén that were conducted or performed, were the Suite for violin, piano and orchestra op. A-1, the Concierto Sinfónico for piano and orchestra op. A-13, Juventus op. A-5, the Symphony Nova Catalònia op. A-17 and a concert version of the first act of Acté, in which the tenor Francesc Viñas made his operatic farewell. In March, 1918, the Symphony Nova Catalònia could also be heard at “Teatro Real” in Madrid, performed by the city's Symphony Orchestra conducted by Enrique Fernández Arbós. In Barcelona, Joan Manen performed as a pianist in a chamber recital on the 25th of June, together with the “Quartet Renaixement” and the soprano Andreua Fornells, playing a selection of his songs, the Mobilis in Mobili Piano Quartet and premiering his Quintet with piano Lui et elle op. A-18.