  We show that thermal noncommutative field theories admit a version of
`channel duality' reminiscent of open/closed string duality, where non-planar
thermal loops can be replaced by an infinite tower of tree-level exchanges of
effective fields. These effective fields resemble closed strings in three
aspects: their mass spectrum is that of closed-string winding modes, their
interaction vertices contain extra moduli, and they can be regarded as
propagating in a higher-dimensional `bulk' space-time. In noncommutative models
that can be embedded in a D-brane, we show the precise relation between the
effective `winding fields' and closed strings propagating off the D-brane. The
winding fields represent the coherent coupling of the infinite tower of
closed-string oscillator states. We derive a sum rule that expresses this
effective coupling in terms of the elementary couplings of closed strings to
the D-brane. We furthermore clarify the relation between the effective
propagating dimension of the winding fields and the true codimension of the
D-brane.
