This Arizona State article suggests that the omnitonic horn and valved horns were invented in the same era and for the same reasons. However, further reading points out the differences between the two. The explanation for their invention is found in Dr. Ericson's article. There is a great illustration of the omnitonic horn. I would hate having to clean that instrument! In 1824 Charles Sax of Brussels designed the most successful of the omnitonic horns. The remainder of the article is devoted to explaining why it was so successful.