Screech sound is generated by the interaction of jet instability waves with the spatially periodic cell structure of a choked supersonic jet, the sound initiating new instability waves at the nozzle. Its frequency is important because of possible structural damage to high-performance aircraft. It was hypothesized that the interaction resulted in a phased array of point sources, with an effective source at distance h′ from the nozzle. This reduced the phase feedback criterion to that of edge tones with frequency f=(U/h′)(N+p)/(1+M), where U, M are, respectively, the velocity and Mach number of the instabilty waves, N is an integer, and p an ideally fixed constant, 0≤p≤1. It was hypothesized that N takes the value yielding maximum feedback for maximum jet instability for edge tones, and that closest to perfect reinforcement, f→fPR=(U/s)/(1+M), s=cell length, for screech. Multiple-source feedback is now considered, allowing for a different (effective) first cell length. The preceding concepts are fully confirmed for screech, but N is not limited to integer values. As illustrated by experimental results, and though f→fPR, absolutely perfect reinforcement is unlikely to occur.