This paper addresses the problem of controlling the enve- lope’s power peak of single carrier modulated signals, band limited by root-raised cosine (RRC) pulse shaping filters, in order to maximize the efficiency of the transmitter’s high power amplifier (HPA). A novel multistage polyphase ap- proach for the magnitude modulation (MM) concept is de- veloped. As opposed to traditional MM solutions, based on look-up-tables (LUT), in this proposal, the MM coefficients are computed in real-time by a low complexity polyphase filter system. The need to use back-off from HPA saturation is almost eliminated (reduction greater than 95%) with just a 2-stage system. Simulation results also show peak-to- average (PAPR) reduction gains similar to the state of the art trellis shaping techniques. However our proposal has the major advantage of allowing this MPMM system to be easily added to any currently working transmitter system to sig- nificantly improve its power efficiency.