  We give a new way to derive branching rules for the conformal embedding
$$(\asl_n)_m\oplus(\asl_m)_n\subset(\asl_{nm})_1.$$ In addition, we show that
the category $\Cc(\asl_n)_m^0$ of degree zero integrable highest weight
$(\asl_n)_m$-representations is braided equivalent to $\Cc(\asl_m)_n^0$ with
the reversed braiding.
