  A recent variant of the inflationary paradigm is that the ``primordial''
curvature perturbations come from quantum fluctuations of a scalar field,
subdominant and effectively massless during inflation, called the ``curvaton'',
instead of the fluctuations of the inflaton field. We consider the situation
where the primordial curvature perturbations generated by the quantum
fluctuations of an inflaton and of a curvaton field are of the same order of
magnitude. We compute the curvature perturbation and its spectrum in this case
and we discuss the observational consequences.
