  Diskoseismology, the theoretical study of normal mode oscillations in
geometrically thin, optically thick accretion disks, is a strong candidate to
explain some QPOs in the power spectra of many black hole X-ray binary systems.
The existence of g-modes, presumably the most robust and visible of the modes,
depends on general relativistic gravitational trapping in the hottest part of
the disk. As the existence of the required cavity in the presence of magnetic
fields has been put into doubt by theoretical calculations, we will explore in
greater generality what the inclusion of magnetic fields has to say on the
existence of g-modes. We use an analytical perturbative approach on the
equations of MHD to assess the impact of such effects. Our main conclusion is
that there appears to be no compelling reason to discard g-modes. In
particular, the inclusion of a non-zero {\it radial} component of the magnetic
field enables a broader scenario for cavity non-destruction, especially taking
into account recent simulations' saturation values for the magnetic field.
