  I review the literature on observational aspects of waves in the solar
chromosphere in the first part of this contribution. High-frequency waves are
invoked to build elaborate cool-star chromosphere heating theories but have not
been detected decisively so far, neither as magnetic modes in network elements
nor as acoustic modes in below-the-canopy internetwork regions. Three-minute
upward-propagating acoustic shocks are thoroughly established through numerical
simulation as the cause of intermittent bright internetwork grains, but their
pistoning and their role in the low-chromosphere energy budget remain in
debate. Three-minute wave interaction with magnetic canopies is a newer
interest, presently progressing through numerical simulation. Three-minute
umbral flashes and running penumbral waves seem a similar acoustic-shock
phenomenon awaiting numerical simulation. The low-frequency network Doppler
modulation remains enigmatic. In the second part, I address low-frequency
ultraviolet brightness variations of the internetwork chromosphere in more
detail. They contribute about half of the internetwork brightness modulation
and presumably figure in cool-star basal flux. They appear to be a mixture of
inverse-contrast granular overshoot at small scales and gravity-wave
interference at mesogranular scales. I present TRACE evidence for the latter
interpretation, and speculate that the low-frequency brightness minima map
canopy heights.
