The complex harmonies of a classical triad

It's a musical chain-reaction: three composers whose lives, fates and music depended on one another to an extraordinary degree. Not immediately obvious, perhaps, when you hear works as different as Camille Saint-Saëns's Carnival of the Animals, Gabriel Fauré's Requiem and Maurice Ravel's Daphnis et Chloé. But without Saint-Saëns's encouragement, Fauré might never have composed a note; nor might he have won the post in which he taught Ravel, who in turn never failed to credit the vital nature of his influence and support.

Saint-Saëns, Fauré and Ravel's interlinked histories are about to be celebrated in style at London's Wigmore Hall, where the cellist Steven Isserlis is assembling a dazzling team to present three concerts featuring the chamber music of these French geniuses.

It all began in 1854 when the nine-year-old Gabriel Fauré arrived in Paris after a three-day coach journey from his home in the south. He was being sent to boarding school at the Ecole Niedermeyer, an establishment that trained musicians for the church. Although little Gabriel was shy, quiet and scared, his southern good looks and charm quickly made him popular, despite his melancholy streak.

In 1861 Saint-Saëns arrived at the school to be its new piano professor. He was a former child prodigy; by the age of ten he had been able to play from memory any one of the 32 Beethoven sonatas. Mercurial and hyper-intelligent, if sometimes cantankerous, he had superb connections, his precocious childhood success having brought him into contact with all the luminaries of Parisian musical life and beyond. He took great delight in introducing them to key figures like Wagner and Liszt, though such dangerous new music was, technically, banned from the school. And he exhorted them to begin composing pieces of their own.

That was why, sitting in the school canteen, Fauré ventured to pen his first song: a setting of Victor Hugo entitled "Le papillon et la fleur". Saint-Saëns, amused by its allegorical story, drew a cartoon of a smug insect and weeping bloom on Fauré's manuscript.

Saint-Saëns was only ten years older than Fauré; they became fast friends and would remain so all their lives. Sometimes Saint-Saëns would take Fauré home with him to the top-floor apartment he shared with his mother and great-aunt. One of his prize possessions was a telescope; the two young composers would go up to the roof and watch the stars through it.

These formative years set a pattern that persisted through all Fauré's professional life: he had Saint-Saëns to thanks for virtually every job he ever won, including the composition professorship at the Paris Conservatoire that brought him so many gifted pupils, Ravel included.

Saint-Saëns's music, too, was among Fauré's vital influences: in the latter's early works, the focused melodies, sweeping élan and imaginative textures are often just a step away from the older composer's style. And Saint-Saëns was not above borrowing from his pupil. Once, when the teenage Fauré left unfinished a setting of the "Tantum Ergo", Fauré's draft became nothing less than the main theme in the first movement of Saint-Saëns's Second Piano Concerto.

When Fauré, after Saint-Saëns's machinations, began to teach at the Paris Conservatoire, he did so often by example. One of Ravel's fellow students, René Kerdyk, recalled: "Fauré used to arrive at the class three quarters of an hour late... His state of reverie was, curiously enough, respected by his pupils, but eventually he would emerge from it and say, in his veiled tone of voice... 'Ravel, play us your Jeux d'eau'... With the final note hanging in the atmosphere like a star, Fauré was uninhibited in his enthusiasm for his young pupil. A few moments went by... The lesson was over. And Enescu, recalling those lightning sessions, added firmly: 'Those were the days when we really made some progress.'"

Despite his absent-minded aspect, Fauré had the rare pedagogic ability to draw out his students' individual "voices". His pupils were composers as different as George Enescu, Florent Schmitt and Nadia Boulanger; each developed a personal, distinctive language – none more so than Ravel. And it was Ravel who accidentally propelled Fauré up from his professorship to the post of the Conservatoire's director. First he was expelled from the Conservatoire for failing to write an acceptable fugue. Then he tried three times, and failed, to win the Prix de Rome, France's most sought-after award. By his third attempt in 1905, Ravel was widely recognised as an important new composer, and, his rejection caused a scandal, during which high-level corruption on the competition jury came to light. Resignations followed, including that of the head of the Paris Conservatoire. As one of the few figures to emerge from the brouhaha looking whiter than white, Fauré – Ravel's mentor, supported by Saint-Saëns's advocacy – was elevated. There he revolutionised the teaching of music, dragging that desperately conservative institution into the 20th century.

Ravel learned vital qualities from Fauré's music: among them balance, control, concision and a sinewy, pure-sounding variety of sensuality. And there is a direct line from Saint-Saëns's scribbled sardonic butterfly adorning Fauré's first song down to the tongue-in-cheek blues in Ravel's Violin Sonata: these composers shared not only artistic sensitivity, but tremendous energy, joy and humour.

Their destinies were intertwined and their music, along with Debussy's, formed the heart of a French school of composition that is essentially still alive, influencing contemporary composers such as Henri Dutilleux. And their music sounds as fresh and vital as it did the day it was written. It is a story well worth celebrating.

Steven Isserlis's Saint-Saëns, Fauré and Ravel concerts are at the Wigmore Hall, London W1 (020 7935 2141) tonight, 15 and 19 November. Jessica Duchen's biography of Gabriel Fauré is published by Phaidon