The Harmonium had a great fortune starting from the second half of the nineteenth century and the first half of the twentieth century. The instrument was immediately adopted in the salons of the upper class together with the piano. Thus a specific literature for this instrument was born, not only in the field of sacred music but also in the profane one. Rossini used it in his "Petite Messe solennelle" to reinforce the accompaniment of the two pianos. The "sei duos" by Camille Saint Saens are dated 1858. The series of pieces presents pieces of extremely different difficulty, from pieces that require a type of virtuoso technique, to pieces with not too advanced techniques. Cesar Franck's "prelude, Fugue et variation", known in it's version for organ only, seems to have been written previously precisely for the harmonium and piano training. This recording gives us a small example of a part ofmusical literature that should rise from the oblivion it had fallen into in recent years.