  We explore the synergy between photometric and spectroscopic surveys by
searching for periodic variable stars among the targets observed by the Apache
Point Observatory Galactic Evolution Experiment (APOGEE) using photometry from
the All-Sky Automated Survey for Supernovae (ASAS-SN). We identified 1924
periodic variables among more than 258000 APOGEE targets; 465 are new
discoveries. We homogeneously classified 430 eclipsing and ellipsoidal
binaries, 139 classical pulsators (Cepheids, RR Lyrae and delta Scuti), 719
long period variables (pulsating red giants) and 636 rotational variables. The
search was performed using both visual inspection and machine learning
techniques. The light curves were also modeled with the damped random walk
stochastic process. We find that the median [Fe/H] of variable objects is lower
by 0.3 dex than that of the overall APOGEE sample. Eclipsing binaries and
ellipsoidal variables are shifted to a lower median [Fe/H] by 0.2 dex.
Eclipsing binaries and rotational variables exhibit significantly broader
spectral lines than the rest of the sample. We make ASAS-SN light curves for
all the APOGEE stars publicly available and provide parameters for the variable
objects.
