  We investigate the possibility that fields coupled to the inflaton can
influence the primordial spectrum of density perturbations through their
coherent motion. For example, the second field in hybrid inflation might be
oscillating at the beginning of inflation rather than at the minimum of its
potential. Although this effect is washed out if inflation lasts long enough,
we note that there can be up to 30 e-foldings of inflation prior to horizon
crossing of COBE fluctuations while still giving a potentially visible
distortion. Such pumping of the inflaton fluctuations by purely conventional
physics can resemble transPlanckian effects which have been widely discussed.
The distortions which they make to the CMB could leave a distinctive signature
which differs from generic effects like tilting of the spectrum.
