Lalo left home at the age of 16 because his father did not want him to be a professional musician. He studied the violin at the Paris Conservatoire, also learning composition privately. While supporting himself as a violinist, performing and giving lessons, Lalo also composed. His early works, published in the 1840s, include pieces for the violin. In the 1850s, Lalo became an important member of a movement to revive chamber music in France. By the mid-1850s, he had already composed two piano trios, which show a considerable mastery of that form. In 1855, Lalo helped found the Armingaud Quartet; this ensemble was created to promote the music of Haydn, Mozart, Beethoven, Schumann, and Mendelssohn. Lalo, who was the quartet's violist and second violinist, composed a string quartet in 1859, thus enhancing his stature as a composer of chamber music. In 1865, Lalo married Julie Bernier de Maligny, a singer who eventually became a leading performer of his songs. Nevertheless, Lalo wished to compose for the stage, and in 1866 he started writing Fiesque, an opera based on Friedrich Schiller's play Fiesko. While Lalo was pleased by his opera, the Paris Opera decided against producing this work. However, despite this setback, Lalo's career flourished. The creation, in 1871, of the Societe Nationale de Musique, whose program was to promote the works of contemporary composers, provided Lalo with an impetus to continue composing for the orchestra. Thus, during the 1870s, Lalo composed several impressive works, including a Violin Concerto in F major, the famous Symphonie espagnole, the Cello Concerto, and the Fantaisie norvegienne for violin and orchestra.
In 1875, Lalo started work on Le Roi d'Ys, an opera based on a Breton legend. Feeling that his work was nearing completion, Lalo offered it to the Opera in 1881. Once again, theaters refused to produce Lalo's work; however, perhaps wishing to somehow compensate the composer, the Opera asked him to compose a ballet. During 1881 and 1882 Lalo wrote Namouna, based on a story from Casanova's Memoires, and the ballet was performed in 1883 to a less-than-appreciative audience. Throughout the 1880s, however, Lalo continued promoting Le Roi d'Ys. The opera was finally performed at the Opera-Comique in 1888, and the reception was extremely favorable. Following this belated triumph, Lalo embarked on several new projects, including Neron, a pantomime, which was performed in 1891. A new opera, La jacquerie, remained unfinished.