It is highly probable that a non-linear resonance between some modes of oscillations in the accretion discs around black holes and neutron stars can play a crucial role in exciting detectable modulations of the X-ray flux.Detailed studies of the resonance models revealed that several of such non-linear resonances are possible in nearly Keplerian discs in stron gravity. Moreover, this idea seems to be strongly supported by observations in all four microquasars showing twin peak QPOs (quasiperiodic oscillations), the ratio of frequency peaks is 3:2.