def draw_staff(expr first, last, offset)=
pickup pencircle scaled stafflinethickness;
for i:= first step 1 until last:
- draw (- interline, (i + offset) * interline) .. (4 interline,( i+ offset)* interline);
+ draw (- staff_space, (i + offset) * staff_space) .. (4 staff_space,( i+ offset)* staff_space);
endfor
enddef;