  Anomalous line shapes of quarkonia are explained naturally as an interference
effect of a $c\bar c$ confined closed channel with the surrounding continua,
well established in other fields of physics as Fano-resonances. We discuss a
quark model coupled-channel analysis describing quarkonium as a mixing of
closed $Q\bar Q$ and molecular-like $D\bar D$ open channels. The asymmetric
line shapes observed in $\psi(3770)$ production cross sections in $e^+e^-$
annihilation to $D^0\bar{D}^0$ and $D^+ D^-$, respectively, are described very
well. The method allows to extract directly from the data the amount of $Q\bar
Q \leftrightarrow D\bar D$ configuration mixing.
