  We present the first reliable calculation of the collective mode structure of
a strongly coupled electronic bilayer. The calculation is based on a classical
model through the $3^{rd}$ frequency-moment-sum-rule preserving Quasi Localized
Charge Approximation, using the recently calculated Hypernetted Chain pair
correlation functions. The spectrum shows an energy gap at $k=0$ and the
absence of a previously conjectured dynamical instability.
