Actually your mother would have seven pedals on her harp - one for each note A-G. The pedals attach to the upper mechanism with steel rods inside the column. The upper mechanism has, if I remember from my tour of Lyon & Healy, over 1500 parts. There are scores of linkages and cams to change the effective length of all of the strings of the same note (A, for example) at the same time. It is a fascinating instrument.