Multiple and altering tonal vibrations are common problem in flexible structures, such as lightweight means of transportation, induced by engine speed/rotor rotations, and their harmonics. A Semi-Active piezoelectric Tuned Mass Damper (SATMD) is developed for the suppression of these excitations, which consists of a resonant mass and a combined springpiezoelectric device connected to an external resistive-inductive electric circuit. The proposed anti-vibration device introduces two anti-resonances to the host structure, which can be manipulated through changes in the shunt impedance, to highly suppress two dominating excitation frequencies or adjust the device to potential frequency fluctuations and maintain its performance. The vibration suppression capabilities of the SATMD are numerically and experimentally demonstrated on a down-scaled simplified airframe model. The anti-vibration device is experimentally proven to effectively adjust its performance to tonal frequency alterations, or to suppress two tonal excitations in distant frequency ranges, even in lower frequency vicinity than the initially tuned auxiliary mass. Finally, one tonal frequency and its 1 st high amplitude harmonic are experimentally shown to be highly suppressed, using a SATMD which adds negligible mass to the structure.