Circular sheet of metal (for use on most types of disc music boxes), cardboard (for use on certain organettes), or composition cardboard-metal (for certain organettes) on which a musical program is arranged in the form of perforations or projections extending from the underside. Almost always easily changed, so that different tunes can be played on the same instrument. * Also spelled disk. * Synonyms (not in popular usage with collectors today, however): record, tune sheet.