abstract: Since 1913, some of the world’s finest trumpeters have utilized the advantages of specialized custom trumpets that can be played in multiple key centers through the operation of additional valves and slides. Merri Franquin (1848-1934), a leading trumpet teacher in twentieth-century Paris, patented two multiple-key trumpets: a four-piston- valve model that plays in the keys of C and D, and a five-piston-valve model that plays in the keys of A, B , C, and D. Thibouville-Lamy (1867-1969), a now-defunct French instrument company, built both models by adding extra valves and slides to three-valve C trumpets. In the mid-1900s, top performers such as Roger Voisin, Armando Ghitalla, and David Hickman began using similar trumpets in performances and recordings. Regrettably, only a privileged few have had access to these instruments and the numerous advantages that they can provide. Thus, by reviewing and building upon current data on multiple-key trumpet design and performance, the author aims to unlock a vast potential for performance enhancement, waiting to be tapped by current and future trumpet performers. / Dissertation/Thesis / Doctoral Dissertation Music 2016