Features =============== The operator DYNA_ALEA_MODAL makes it possible to calculate the response in the frequency domain, on a modal basis, of a structure subjected to an excitation represented by an interspectral matrix (conferdefi_inte_spec [:external:ref:`U4.36.02 `]). The magnitude of excitement may be of the type of imposed ddl or effort associated with a degree of freedom. It can also correspond to sources of fluid excitation [:ref:`R4.05.02 `]. The excitation can be given in derivative form with an order equal to 0, 1 or 2 (displacement, speed or acceleration). The operator RESt_spec_PHYS [:external:ref:`U4.63.22 `] makes it possible to restore the response when moving or in effort to the degrees of freedom "of observation" (node pair, component). The interspectral modal response matrix thus calculated can be reintroduced into a new calculation.