  The observer's frame is the more elementary description of the gravitational
field than the metric. The most general covariant, even-parity quadratic form
for the frame field in arbitrary dimension generalises the New General
Relativity by nine functions of the d'Alembertian operator. The degrees of
freedom are clarified by a covariant derivation of the propagator. The
consistent and viable models can incorporate an ultra-violet completion of the
gravity theory, an additional polarisation of the gravitational wave, and the
dynamics of a magnetic scalar potential.
