Johann Vexo is a world class organist of phenomenal talent and ability and performs here on the world famous grand organ of Notre-Dame Cathedral in Paris, where he's the organist of the choir organ and where Louis Vierne was organiste-titulaire from 1900 until his death in 1937 (at the organ).

Vierne's 2nd Symphony for organ was inspired by the sound of this instrument in its magnificent acoustical setting, and this Allegro is this Symphony's first movement.

In recognition of Vierne's many accomplishments as a virtuoso performer, composer, and teacher, and that Dr. Monrotus is a great great grandson of his, tutorially, Dr. Monrotus dedicated his own Prelude Internationale Op. 5 to the memory of Vierne [See menu bar, Free Stuff] and composed it using some of Vierne's methods, including the 6 part form that Vierne taught his own students for improvisation on a free theme. 

This video is one of the finest demonstrations of artistic interpretation and economy of motion by an organist anywhere on the internet, and we thank Mr. Vexo for recording and posting it for public viewing.   

This is how it's done, folks.