If we endow the torus $Y={{\bf R}}^{n}/{{\bf Z}}^{n}$ with a flat metric and consider only flat Lagrangian subtori in $X^{\vee}$ then all higher compositions in the $A_{\infty}$-pre-category $FO(X^{\vee})$ can be written in terms of explicit “truncated theta series” analogous to those considered in [Ko] and [P1] in the case of elliptic curves.