  We continue the study of power corrections for $N$-jettiness subtractions by
analytically computing the complete next-to-leading power corrections at
$\cal{O}(\alpha_s)$ for color-singlet production. This includes all
nonlogarithmic terms and all partonic channels for Drell-Yan and gluon-fusion
Higgs production. These terms are important to further improve the numerical
performance of the subtractions, and to better understand the structure of
power corrections beyond their leading logarithms, in particular their
universality. We emphasize the importance of computing the power corrections
differential in both the invariant mass, $Q$, and rapidity, $Y$, of the
color-singlet system, which is necessary to account for the rapidity dependence
in the subtractions. This also clarifies apparent disagreements in the
literature. Performing a detailed numerical study, we find excellent agreement
of our analytic results with a previous numerical extraction.
