The idea of increasing the number of resonance conditions of a cantilever piezoelectric harvester by coupling the harvester with a frame that surrounds the harvester’s body is presented and discussed. Experimental tests on prototypes show that it is possible to design framed harvesters able to generate significant powers at two frequencies. Since the framed harvesters will be used for harvesting energy from periodic vibrations characterized by multiple harmonics, a tuning method is needed. For this reason a numerical sensitivity analysis is performed to analyze the effect on harvester tuning of small masses mounted on the frame. A prototype tuned to 40 and 80 Hz is developed and tested, its performance is compared with the one of a system of two simple harvesters tuned to the same frequencies.