  I review recent work that goes beyond our model for the Low-Frequency
Quasi-Periodic Oscillation of microquasars, based on the Accretion-Ejection
Instability. I show that similar instabilities, which can be viewed as strongly
unstable versions of the diskoseismologic modes, provide explanations for both
the High-Frequency QPO and for the quasi-periodicity observed durng the flares
of Sgr A*, the supermassive black hole at the Galactic Center.
