We investigate the dynamics of the 3 DOF model of two self-excited pendula suspended on the oscillating beam. The research is focused on the analysis of possible multistability of the synchronous configurations. The regions of different behaviours (both unique, as well as the co-existing ones) are shown and the influence of the model’s parameters on their occurrence is studied. We exhibit, that the pendula can synchronize in a classical phase-locked way (apart from the in-phase and the anti-phase patterns) and the phase shift between them strictly depends on the angle at which the beam oscillates. The basins of attraction of different solutions are discussed and the conditions leading to the desired states are indicated. The bifurcation analysis of the system shows possible scenarios of transitions between various attractors, which are supported by the energy diagrams determining the energy flows for the dynamical elements. We apply the probability methods to measure the basin stability of possible states and to estimate their occurrence, when the initial conditions are uncertain. Our results have been obtained for both identical, as well as non-identical pendula and we describe the phenomena that can be observed in various models of classical mechanics in general.