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This paper presents the experimental study of the phenomenon of a pair of two parallel free-to-rotate cylinders submitted to an accelerating cross flow and the resulting wake flow. A fixed pitch-to-diameter ratio P/D = 1.26 was adopted. The study was performed in an aerodynamic channel using hot wires anemometers synchronized to a high-speed digital camera. The flow was accelerated from rest to velocities of 5.4 and 10.0 m/s, corresponding to Reynolds numbers computed with the tube diameter of 9.00 × 103 and 1.66 × 104, respectively. Time series of velocity and angular position of the cylinders were analyzed by Fourier and wavelet transforms. The time series of the angular position of the cylinders were obtained from the digital movies. Preliminary velocity measurements performed with fixed cylinders positioned side-by-side indicated the presence of a bistable flow for both Reynolds numbers investigated, characterized by two levels of velocity without a defined pattern. In the free-to-rotate configuration, an oscillating movement of the cylinder set starts as the flow velocity increases. This oscillation was followed by a rotational movement, without a defined direction. In this case, high turbulence intensity is present in the flow as the cylinders oscillate, being reduced as the cylinder set starts to rotate, and the flow reaches a steady-state condition. [ABSTRACT FROM AUTHOR]