After the stay in the villa Medici in Rome associated with the prize, he made his debut as a composer in Paris with the "poème sacré" La Nativité (1875). He then composed several operas, ballets and dramatic music, another "drame sacré", choral and orchestral works, songs, chamber music pieces and motets. His first opera Les Amoureux de Catherine was performed for the hundredth time in 1889 and was given until 1920. Maréchal's compositional style is often characterized by chromaticism, his musical expression simple, but dramatic and effective.
He also wrote music-critical articles for Le Figaro and published several volumes of Memories and in 1910 the Monographie universelle de l'Orphéon. He corresponded with the composer Marguerite Olagnier.