  Quantum oscillations in a tilted magnetic field offer the possibility of
distinguishing singlet versus triplet order parameters in the particle hole
channel provided the measurements reflect a putative ``normal'' state of a
density wave obtained by applying by high magnetic field at low temperatures. A
theoretical analysis is given that compares spin density wave, a singlet
$d$-density wave, and a triplet $d$-density wave. While the existence of a spin
zero in the oscillation amplitude is a necessary consequence of a singlet order
parameter, a triplet order parameter may or may not exhibit a spin zero, making
it a quantitative issue that depends on the actual extremal orbits on the Fermi
surface. Nonetheless, a theoretical analysis can shed light on the striking
recent measurements in $\mathrm{YBa_{2}Cu_{3}O_{6+\delta}}$.
