Perhaps the one aspect of Franck's career which blends his gifts as both a composer and a teacher was as an organist in the loft at Sainte-Clotilde. Here was combined both his instincts and creative energies as a composer with his insights, observations, and ability to inspire as a teacher. Nowhere is his skill as an organist better documented than in the many accounts left to the modern reader of Franck the improviser. In these histories and memoires we also learn of Franck the teacher and composer, whether it in the classroom at the Conservatoire, as a concert organist playing throughout Paris, or the organ loft at Sainte-Clotilde. His one time student and successor at the basilica, Gabriel Pierné, recounts the master's improvisation:

Also, the famous organist and pupil of Franck, Charles Tournemire, stated that: “The art of improvisation was carried to an extraordinary degree. He taught unstintingly by his own example [Tournemire's emphasis].” Louis Vierne, also a student and fortunate guest in the loft at Sainte-Clotilde, remarked insightfully:

Here the instances of Père Franck teaching by example as he improvised on the organ are powerful. These stories recount his ability to create music instantaneously that was not only original, but logical, precise, and what by all accounts were well-constructed, fully-developed compositions, attesting to his great skills as an organist and composer. Imagine the weekly opportunities to hear Franck mprovise and create music in the organ loft which was so ephemeral that it was never heard again. Tournemire captured this sentiment exactly when he remarked: “For thirty years he built monuments in sound which are lost to us forever.”