These fascinating instruments are connected to fascinating biografies - and the one of Leon Leblanc is a good start to understand in which spirit these instruments were built.
Leon Leblanc, born November 24, 1900, in La Couture-Boussey to Georges Leblanc, wind instrument maker—successor to Denis Toussaint Noblet (1850–1919), and Laure Clémence Jeuffroy (1875–1965), a worker "in musical instruments," Léon Leblanc was surrounded by music from a very early age. Leblanc's childhood was spent in the workshops, in contact with workers, machines, wood, and the musicians of the village band that his father, Georges, a bassoonist, led. When he was six years old, he began to learn the soprano saxophone, and then moved on to the clarinet. He was sent to the Collège Saint-Nicolas de Paris to further his studies, and, at 16, he earned his Brevet Élémentaire (a school certificate requiring two years of elective study). 1921 was the pivotal year: after earning his clarinet diploma at the Paris Conservatoire, Leblanc travelled in the United States for three months to display the Noblet-Leblanc clarinets, and soon realized the potential of the North American market. {...}
An enterprising and visionary son and a father oriented toward the future: these are the ingredients of success. In the mid-1920s, new three-story workshops were built in the Belleville district at 70 rue des Rigoles in the 20th arrondissement of Paris. It was thanks to Charles Houvenaghel (1878–1966), top-class acoustician, clarinetist, and friend of the Leblancs, that experiments and acoustic tests became widespread. They also opened up the way to modernity and to developing higher-performance instruments. Leblanc and Houvenaghel invented, patented, and manufactured models of clarinets to be able to form an entire orchestra, from the sopranino to the contrabass.
{SOURCE: Léon Leblanc (1900–2000), music as a vocation, Léon Leblanc (1900–2000), music as a vocation - Google Arts & Culture}
THE FIRST LEBLANC SAXOPHONE: Continuing the heritage of Adolphe Sax
In 1926, Leon Leblanc also filed the patent for a new Saxophone, called "Le Rationnel", 'the Logical'; Patent US1840456: Saxophone, granted in 1932. Dutch researcher and saxophone builder Marten Postma has shown strong similarities with the final patent by Adolphe Sax from 1881 for an alto saxophone keyed to high G with already similar keywork inventionsand is convinced that this heritage of Adolphe Sax was present to Leblanc and Houvenaghel. Sax himself was never able to realize this patent fully and built only one prototype, Ad. Sax alto saxophone 40842. {Leblanc Rationnel and patent 1840456}. Both Adolphe Sax and Charles Houvenaghel searched for ways to build saxophones truthfully to the fundamental principle of Charles Boehm: no key cup below an open tone hole should be closed to allow the most free and undisturbed sound on each note resulting in an equal chromatic scale of the saxophone. In conventional saxophones following the Adolphe Sax design, Low C#, Eb, G# remain closed and on cross-fingerings for middle C, Bb and F# were common which sounded muffled and created instabilities in intonation.