The claviorgan is an instrument that has long been neglected by Organologists, and considered a mere oddity in the history of stringed-keyboard instruments. However, the combination of strings and pipes in a single entity permeates musical history from the late-1400s through to present day in a variety of guises. The thesis will present a new nomenclature using the term claviorgan as an ‘umbrella term’ under which a variety of different combinations of stringed-keyboard and pipes will be considered and defined: this recognises that there are distinct trends in instrument building, and different probable uses for the various claviorgans. Through a series of case-studies of building-schools and epochs, the thesis will consider both the written evidence for combination instruments from published musical theory books and from other documentary evidence, as well as the evidence from the surviving instruments. It is not the intention to provide detailed organological studies of surviving instruments, as there are not enough examples from many of the building schools to make a reasonable comparison. However, these instruments will be considered in terms of their status, their owners, and in particular the balance between the elements. Little or no music has survived that was written specifically to exploit claviorgans, and the thesis examines the possible reasons for this lack of music in light of keyboard repertoire in general, and the lack of distinction between music for harpsichord and organ in the greater part of music history. The thesis also discusses the concept of solo music versus accompaniment and continuo, with a particular focus on the claviorgan as an instrument for ensemble performance as evidenced by contemporary descriptions of their use and by the status the instruments held. This discussion will be followed and complemented by an appendix of surviving instruments and references to combination instruments compiled by the author.