The flow of premixed reactants in a duct with flames stabilized on a sudden expansion and an open downstream end gave rise to combustion oscillations of low frequency due to extinction and relight and high frequency due to longitudinal acoustic modes. This paper quantifies the flammability and stability limits and their temperature dependence; considers the nature of oscillations, their coupling and modulation effects with methane, propane and ethylene; and describes the extent to which they can be reduced in amplitude by oscillations imposed at discrete frequencies with and without active phase control and with the addition of small quantities of fuel close to the expansion.