key frame

Device mainly used on fairground organs and dance organs but used on many other types of instruments as well. Contains a series of spring-loaded brass or steel levers. When one end of a lever pops up through a hole in a cardboard music book (also listed in this Glossary), the other end of the lever or key opens an aperture which actuates a pneumatic action. The folding cardboard music book is pulled through the key frame by rubber pinch rollers. A durable system capable of withstanding rugged use; one which is resistant to humidity changes. For these reasons most very large fairground organs and dance organs of European manufacture use the key frame system. (Compare to keyless frame.)