The authors describe measurements of nonlinear interactions between drift waves and low-frequency flute-like modes in the UMIST quadrupole. They present experimental measurements of the bispectrum, and also results from a technique of 'amplitude correlation' which they believe provides a more direct way of determining the direction of the energy flow. On the basis of the results they propose a model of energy flow in the drift-wave spectrum: the observed spectrum contains regions of growth at high frequency and damping at low frequency, with flow down the spectrum via a cascade mediated by the flute-like modes.