Parameters of a sweep signal that controls operation of a marine non-impulsive source can be set. Setting the parameters can include selecting a stop frequency of the sweep signal, defining a taper of the sweep signal, and adjusting an initial phase of the sweep signal. The parameters can be set such that a magnitude of an amplitude spectrum of a combined output of a marine impulsive source and the marine non-impulsive source is greater than or equal to a magnitude of an amplitude spectrum of a marine impulsive source output at frequencies below the stop frequency. A controller of the marine non-impulsive source can be programmed with the sweep signal having the parameters set to control the marine non-impulsive source.