  We determine the mass dependence of the coupling constant for N=2 SYM with
N_f=1,2,3 and 4 flavours. All these cases can be unified in one analytic
expression, given by a Schwarzian triangle function. Moreover we work out the
connection to modular functions which enables us to give explicit formulas for
the periods. Using the form of the J-functions we are able to determine in an
elegant way the couplings and monodromies at the superconformal points.
