  We investigate the nature of tidal effects in compact triple-star systems.
The hierarchical structure of a triple system produces tidal forcing at high
frequencies unobtainable in binary systems, allowing for the tidal excitation
of high frequency p-modes in the stellar components. The tidal forcing exists
even for circular, aligned, and synchronized systems. We calculate the
magnitude and frequencies of three-body tidal forcing on the central primary
star for circular and coplanar orbits, and we estimate the amplitude of the
tidally excited oscillation modes. We also calculate the secular orbital
changes induced by the tidally excited modes, and show that they can cause
significant orbital decay. During certain phases of stellar evolution, the
tidal dissipation may be greatly enhanced by resonance locking. We then compare
our theory to observations of HD 181068, which is a hierarchical triply
eclipsing star system in the Kepler field of view. The observed oscillation
frequencies in HD 181068 can be naturally explained by three-body tidal
effects. We then compare the observed oscillation amplitudes and phases in HD
181068 to our predictions, finding mostly good agreement. Finally, we discuss
the past and future evolution of compact triple systems like HD 181068.
