Alto sax, "semi-rationnel" model front

This is a specific model produced by Leblanc, manufactured between 1931 and 1975 in only 122 copies. It is a simplified version of the Rationnel Intégral system devised in 1931 by Charles Houvenaghel, a brilliant acoustician working at the Leblanc workshop. The complicated keywork based on the Boehm system meant the keys could be actioned independently, without requiring the use of fingerings involving the forks and thus meaning the musician could play virtuosic passages and ornaments, such as trills and tremolos, at great speeds. While technically brilliant, the two systems never gained popularity among the public due to the greatly increased weight of the instruments, the necessity of very careful fine-tuning of the keys, and the need to learn a new fingering.