These pages comprise a dictionary of terms relating to the pipe organ. Please keep definitions to a few sentences, and do not include pictures or sound clips. When more space is needed for a term, a new page can be created for it. Diapason [noun] a family of organ tone which is not imitative of any other instrument, comprised of open cylindrical metal pipes. Diapason stops are the backbone of the organ ensemble and will appear at several pitch levels and usually in every division of the instrument. Also, a stop of diapason tone. Diaphone Disc Double Touch Drums Dulzian Duplex Action