Each dance and its tune is in a file with a name of the form PPN_Title.abc, where PP is the 2-digit page number, N is 1 or 2 for the position on the pate, and the title (all but initial articles) has underscores where the spaces are. Within the file, the X: index number is the number found on the page beneath the tune's key/time signatures. These numbers were contiguous across all (most?) of the Thompsons' "24 Country Dances for the Year ..." series of dance booklets.