  We present a large-scale numerical study, supplemented by experimental
observations, of a quasi-two-dimensional active system of polar rods and
spherical beads confined between two horizontal plates and energised by
vertical vibration. For low rod concentrations $\Phi_r$ we observe a direct
phase transition, as bead concentration $\Phi_b$ is increased, from the
isotropic phase to a homogeneous flock. For $\Phi_r$ above a threshold value,
an ordered band dense in both rods and beads occurs between the disordered
phase and the homogeneous flock, in both experiments and simulations. Within
the size ranges accessible we observe only a single band, whose width increases
with $\Phi_r$. Deep in the ordered state, we observe broken-symmetry "sound"
modes and giant number fluctuations. The direction-dependent sound speeds and
the scaling of fluctuations are consistent with the predictions of field
theories of flocking, but sound damping rates show departures from such
theories. At very high densities we see phase separation into rod-rich and
bead-rich regions, both of which move coherently.
