The retirements of both Meifred and Gallay in 1864, coupled with some restructuring of the Conservatoire by its administration, had a profound effect on the horn class. The result had two threads: first, the study of horn was restricted to the natural horn, taught by Jean Baptiste Victor Mohr, a former student of Gallay, and a willing proponent of the old instrument. The second thread involved the Gymnase de musique militaire, which had gone on a brief hiatus in the 1850s, and was later revived as a separate entity in support of band music, and thus of certain valved instruments. This chapter looks at Mohr and his method (1869), the factors surrounding the revival of the Gymnase, and the work of various others, including cornet soloist Jean-Baptiste Arban and composer Camille Saint-Saëns, in support of valved instrument instruction. Just before Mohr unexpectedly died, a panel comparison was held at the Conservatoire that considered the “appropriate” use of the valved horn. Eventually, Mohr’s successor, François Brémond, convinced the administration to move the instruction from the natural horn to the valved horn, and composed a method for the “new” instrument.