The class he inherited was initially stunned by this new teacher, who suddenly demanded a formidable technique and a knowledge of J. S. Bach's organ works as prerequisites to effective improvisation.

Widor had several students in Paris who were to become famous composers and organists in their own right, most notably the aforementioned Dupré, Louis Vierne, Charles Tournemire, Darius Milhaud, Alexander Schreiner, Edgard Varèse, Hans Klotz, and the Canadian Henri Gagnon.

Albert Schweitzer also studied with Widor, mainly from 1899; master and pupil later collaborated on an annotated edition of J. S. Bach's organ works, published in 1912 – 1914.

Among the leading organ recitalists of his time, Widor visited many different nations in this capacity, including Russia, England, Germany, the Netherlands, Portugal, Italy, Poland, and Switzerland.

He was named to the Institut de France in 1910, and was elected "Secrétaire perpetuel" (permanent secretary) of the Académie des Beaux-Arts in 1914, succeeding Henry Roujon.

His close friend, Isidor Philipp gave piano lessons there, and Nadia Boulanger taught an entire generation of new composers.

Widor wrote music for a wide variety of instruments and ensembles (some of his songs for voice and piano are especially notable) and composed four operas and a ballet, but only his works for organ are played with any regularity today.

The organ of the Baroque and Classical periods was designed to project a clear and crisp sound capable of handling contrapuntal writing.

This new style of organ, with a truly orchestral range of voicing and unprecedented abilities for smooth crescendos and diminuendos, encouraged composers to write music that was fully symphonic in scope.

This trend was not limited to France, and was reflected in Germany by the organs built by Friedrich Ladegast and the works of Franz Liszt, Julius Reubke, and Max Reger.

With the Opus 42 symphonies, Widor shows his mastery and refinement of contrapuntal technique, while exploring to the fullest the capabilities of the Cavaillé-Coll organs for which these works were written.

They also honored, respectively, the Gothic Church of St. Ouen, Rouen and the Romanesque Basilica of St. Sernin, Toulouse, with the new Cavaillé-Coll organs installed in each.

Dating from this same period, and also based on a plainsong theme, is the "Salve Regina" movement, a late addition to the much earlier second symphony.

5, a toccata, which is often played as a recessional at wedding ceremonies and at the close of the Christmas Midnight Mass at Saint Peter's Basilica, Vatican City.

5 is the first of the toccatas characteristic of French Romantic organ music, and served as a model for later works by Gigout, Boëllmann, Mulet, Vierne and Dupré.

Widor was pleased with the worldwide renown this single piece afforded him, but he was unhappy with how fast many other organists played it.