Recent data from the DESI galaxy survey suggest that the dark energy (DE) equation of state w(z) might be time-dependent and cross the phantom divide w=−1. I will consider two-fluid DE models designed to exhibit a similar behaviour. Sound modes in the DE fluids imprint a scale-dependent bias in the clustering of biased tracers of the large scale structure. I will present a computation of this effect and discuss the prospects for its detection. If time permits, I will show that sound wakes induced by the motion of dark matter halos relative to the DE fluids imply a (weak) bound cs2≳10−5 on the DE sound speeds.