  We present our models of the effect of binaries on high-resolution
spectroscopic surveys. We want to determine how many binary stars will be
observed, whether unresolved binaries will contaminate measurements of chemical
abundances, and how we can use spectroscopic surveys to better constrain the
population of binary stars in the Galaxy. Using a rapid binary-evolution
algorithm that enables modelling of the most complex binary systems we generate
a series of large binary populations in the Galactic disc and evaluate the
results. As a first application we use our model to study the binary fraction
in APOGEE giants. We find tentative evidence for a change in binary fraction
with metallicity.
