  KIC 8569819 is an eclipsing binary star with an early F primary and G
secondary in a 20.85-d eccentric orbit. The primary is a delta Sct - gamma Dor
star pulsating in both p modes and g modes. Using 4 years of Kepler Mission
photometric data we independently model the light curve using the traditional
technique with the modelling code PHOEBE, and we study the orbital
characteristics using the new frequency modulation (FM) technique. We show that
both methods provide the equivalent orbital period, eccentricity and argument
of periastron, thus illustrating and validating the FM technique. In the
amplitude spectrum of the p-mode pulsations we also discovered an FM signal
compatible with a third body in the system, a low mass M dwarf in an 861-d
orbit around the primary pair. However, the eclipses show no timing variations,
indicating that the FM signal is a consequence of the intrinsic change in
pulsation frequency, thus providing a cautionary tale. Our analysis shows the
potential of the FM technique using {\it Kepler} data, and we discuss the
prospects to detect planets and brown dwarfs in Kepler data for A and F stars
even in the absence of transits and with no spectroscopic radial velocity
curves. This opens the possibility of finding planets orbiting hotter stars
that cannot be found by traditional techniques.
