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Summary form only given. Due to the increasing bandwidth of Traveling Wave Tube Amplifiers (TWTAs), broadband klystrons, and the possibility of electron-beam modulation using Field Emitter Arrays (FEAs), there has been a resurgence of interest in understanding the electron beam-wave interaction when the beam and wave initially have multifrequency content. In the case of the klystron, this corresponds to understanding how the electron beam propagates a multitonal velocity or density disturbance. In a distributed interaction device like the TWTA the beam dynamics, and hence radiation dynamics, are further complicated since a beam electron interacts with a forcing field on the circuit for its entire trip through the device. We choose the simpler device, an idealized broadband klystron model, to study harmonic and intermodulation distortions in the multifrequency beam-wave system. The beam dynamics are modeled by nonlinear fluid equations, and the question of how the beam propagates general (multitonal) input conditions is addressed. Although the question has been considered before in some generality, we simplify the beam model and consider specifically multitonal excitation as would be used in a communications application.