[4] He also was the founder, and, until his death, the conductor of the celebrated concerts attached to the conservatory of Brussels, and he inaugurated a free series of lectures on musical history and philosophy.

[3] Fétis produced a large quantity of original compositions, from the opera and the oratorio to the simple chanson, including several musical hoaxes, the most famous of which is the "Lute concerto by Valentin Strobel", premiered with Fernando Sor as soloist.

The work is attributed not to the Alsascian lutenist Valentin Strobel, but to Jean (Johann) Strobach, a member of a prominent Bohemian family of musicians.

[5] Fétis had the privilege to have Niccolò Paganini, Robert Schumann, and Hector Berlioz as contemporaries and to work with the violin maker and dealer, Jean-Baptiste Vuillaume.

[3] While Fétis's critical opinions of contemporary music may seem conservative, his musicological work was ground-breaking, and unusual for the 19th century in attempting to avoid an ethnocentric and present-centered viewpoint.

[3] His pupils included Luigi Agnesi, Jean-Delphin Alard, Juan Crisóstomo Arriaga, Friedrich Berr, Louise Bertin, William Cusins, Julius Eichberg, Ferdinand Hérold, Frantz Jehin-Prume, Jacques-Nicolas Lemmens, Adolphe Samuel, Charles-Marie Widor, Hippolyte André Jean Baptiste Chélard, Émile Bienaimé, Théodore Labarre, Louis van Waefelghem, Federico Consolo, Jean-Grégoire Pénavaire [fr], Jan Van den Eeden [fr], François Riga [nl], Charles Baetens [ca], Stanisław Duniecki [pl], and José Parada y Barreto [es].

In the Revue musicale issue of 1 February 1835[6] he wrote of the Symphonie Fantastique: I saw that melody was antipathetic to him, that he only had a faint notion of rhythm; that his harmony, formed by an often monstrous accretion of notes, was nevertheless flat and monotonous; in a word I saw that he lacked melodic and harmonic ideas, and I judged that he would always write in a barbarous manner; but I saw that he had the instinct for instrumentation, and I thought that he could fulfil a useful vocation in discovering certain combinations that others would put to better use than he.

In other words, a man like Beethoven could not possibly fail to be in entire agreement with the harmonic theories of M. Fétis.Troupenas did in fact remove Fétis' editorial marks, but Berlioz was still unsatisfied.

He went on to criticize Fétis in one of the monologues of Lélio, ou le Retour à la vie, the 1832 sequel to Symphonie Fantastique: These young theorists of eighty, living in the midst of a sea of prejudices and persuaded that the world ends with the shores of their island; these old libertines of every age who demand that music caress and amuse them, never admitting that the chaste muse could have a more noble mission; especially these desecrators who dare lay hands on original works, subjecting them to horrible mutilations that they call corrections and perfections, which, they say, require considerable taste.

Assembled from individual articles that Fétis published in the Revue et Gazette musicale de Paris around 1840, the book predates Hugo Riemann's more well known Geschichte der Musiktheorie by fifty years.

In the Musik-Lexicon of 1882, Hugo Riemann states that "to [Fétis'] meditations we are indebted for the modern concept of tonality…he found himself emancipated from the spirit of a particular age, and able to render justice to all the various styles of music."

Though some other theorists, most notably Matthew Shirlaw,[10] have had decidedly negative views, Riemann's assessment captures the two key features of Fétis' text.

He claimed that "tonalité" is the primary organizing agent of all melodic and harmonic successions and that the efforts of other theorists to find the fundamental principle of music in "acoustics, mathematics, aggregations of intervals, or classifications of chords have been futile.

[14] In his comparative work, Fétis attempted "a new method of classifying human races according to their musical systems"[15] following contemporary trends of social darwinism in the emerging fields of ethnology and anthropology.

However, if one wishes to interpret Fétis' metaphysical theory, one of his unique theoretical ideas is laid out in book 3 of the Traité complet, that of harmonic modulation.

Though Liszt may have been an open disciple of the ideas of the Omnitonic and Omnirhythmic, the influence of such thinking can perhaps be seen most clearly in the music of Brahms, where hemiola and mixing of time signatures is a common occurrence.

The original Italian text for the song (Se i miei sospiri) was found set to different music by Alessandro Scarlatti in his 1693 oratorio "The Martyrdom of St.