Stimulation treatments for various medical disorders comprise serially varying the stimulation parameters, especially in order to treat multiple symptoms of a disorder. Roving of parameter values can be done in relation to the proportional incidence of the symptoms. Varying the parameters can occur according to algorithms designed in relation to endogenous rhythms of a patient. Especially when using low-frequency stimulation signals the parameter values can be set in order to match or avoid these internal activity patterns and rhythms. These treatment strategies thereby improve the therapeutic efficacy of stimulation or and decrease risk of interference with normal brain, sensory, motor, and cognitive processes. Novel methods are described for choosing, creating and subsequently stimulating with partial signals having unique temporal and spectral profiles which summate to produce desired vector fields, and which may be roved to produce roving vector fields. Stimulation can occur using different devices such as implantable devices or transcranial magnetic stimulators.