Jean-Philippe Rameau, portrait attributed to Jacques Aved. Via Wikimedia Commons (public domain).
The first sentence is a declaration of war: music is the science of sounds. It opens the Traité de l’harmonie that Jean-Philippe Rameau published in Paris in 1722, at thirty-eight, when he was still a provincial organist without a single opera to his name. The book would make him famous before his music did, and for once fame got it right: it is the treatise that organised the way the West thinks about chords, and in some respects still does.
The central idea is one of those that seem obvious afterward. Before Rameau, a chord was a blend of intervals counted up from the bass, and every arrangement was a case of its own. Rameau says: no, C-E-G, E-G-C and G-C-E are the same chord in three different outfits, and its true name lies in the basse fondamentale, the root, even when it is not the lowest note you hear. From this insight descends the whole theory of chords and inversions studied in conservatories today, and also the way a pop guitarist reads chord symbols: when he writes a C over a staff, he is using Rameau without knowing it.
Alessandro Baricco, in the Breve storia eretica della musica classica that sits in the Melos library, calls the Treatise the Bible of musical agriculture: the moment when sounds stop being gathered wherever they happen to grow and are fenced in, catalogued, cultivated. The metaphor is fertile because it holds together the two faces of the operation. On one side the gain, enormous: a simple, learnable harmonic language with which, within twenty years, anyone in Europe could write and understand music, and on which were built the symphony and sonata form. On the other side the loss: a world of unclassified sounds that was left outside the fence, and whose absence contemporaries felt at once, not three centuries later.
Rameau spent the rest of his life defending and correcting his own system, quarrelling with half a century of French intellectuals, Rousseau first among them, and fifteen years later he also took on the responsibility nobody wanted: declaring that equal temperament, which divides the octave into twelve equal parts all slightly out of tune, was the lesser evil on which to found musical practice. He was right, in the bluntest sense: it is the system to which every piano you have ever heard is tuned. The Treatise is in the Melos library, on the shelf of scores and historical treatises, in a reproduction of the original edition: six hundred dense pages that begin with a single sentence, and that sentence won.