  DR Tau has been noted for its unusually high variability in comparison with
other T Tauri stars. Although it is one of the most extensively studied
pre-main sequence stars, observations with millimeter interferometry have so
far been relatively limited. We present NOEMA images of $^{12}$CO, $^{13}$CO,
C$^{18}$O, SO, DCO$^+$, and H$_2$CO toward DR Tau at a resolution of
$\sim0.5''$ ($\sim100$ au). In addition to the protoplanetary disk, CO emission
reveals an envelope, a faint asymmetric outflow, and a spiral arm with a clump.
The $\sim1200$ au extent of the CO arm far exceeds that of the spiral arms
previously detected in scattered light, which underlines the necessity of
sensitive molecular imaging for contextualizing the disk environment. The
kinematics and compact emission distribution of C$^{18}$O, SO, DCO$^+$, and
H$_2$CO indicate that they originate primarily from within the Keplerian
circumstellar disk. The SO emission, though, also exhibits an asymmetry that
may be due to interaction with infalling material or unresolved substructure.
The complex environment of DR Tau is reminiscent of those of outbursting FUor
sources and some EXor sources, suggesting that DR Tau's extreme stellar
activity could likewise be linked to disk instabilities promoted by large-scale
infall.
