<p>In the turbomachinery design, non-synchronous vibration (NSV), observed primarily in the front stages of high-pressure compressors and fan blades, is a dangerous aeroelastic phenomenon resembling flutter response. However, typical flutter stability parameters (e.g., reduced frequency, incidence angle, Mach number) remain in regions that are stable. Experimental data and computational studies indicate that NSV arises from a combination of coherent aerodynamic instabilities and blade motion. When the frequency of a coherent flow instability approaches the natural frequency of the blade, lock-in can occur, potentially leading to premature high-cycle fatigue failures. While much prior work has focused on tip-clearance effects or rotating machinery, experimental studies on isolated profiles are limited. The current study investigates the coherent instabilities in flow past an isolated profile, potentially leading to non-synchronous vibration, by experimental techniques. In a test rig designed for the investigation of flutter in a linear blade cascade, an isolated compressor blade profile was mounted at incidence angles between 5–40&#xa0;deg and Mach numbers ranging from low incompressible to transonic flow regimes. The blade was instrumented with miniature Kulite pressure transducers with pressure ports distributed on the suction side of the blade. In addition to unsteady pressure measurements, the flow field and shock wave structure near the blade was recorded using shadowgraphic and schlieren techniques with a high-speed camera. For certain low angles of attack, a weakly irregular flow instability is detected as a result of the normal shock oscillation. At medium angles of attack, the spectra of the Kulite pressure transducers contain a single peak roughly corresponding to the frequency of Strouhal vortex shedding between 650–750 Hz. At high angles of attack and Mach numbers, Strouhal vortex shedding disappears and a new peak occurs in the spectra at a significantly lower frequency below 100 Hz. This low-frequency peak appears to be caused by oscillation of the separation zone boundary, which forms a convergent-divergent channel and accelerates the flow to a supersonic velocity. Based on the results with a fixed blade, a configuration was selected in which periodic vortex shedding occurs at a relatively low frequency. In this configuration, a series of measurements was finally performed with a blade undergoing externally excited torsional oscillations with an external excitation frequency close to the fluid instability frequency. The system revealed a behavior typical for non-synchronous vibrations encountered in turbomachinery: outside of the lock-in region, the unsteady pressure spectrum contains two distinct peaks, corresponding to the fluid instability frequency and structural frequency. Within the lock-in region, the fluid instability changes behavior, adjusts to the structural frequency and demonstrates itself as a single and significantly stronger peak in the pressure spectrum.</p>