  We present a complete analysis of the linearised dynamics of active solids
with orientational order, taking into account a hitherto overlooked consequence
of rotation invariance. Our predictions include the possibility of stable
active solids with quasi-long-range order in two dimensions and long-range
order in three dimensions, generic instability of the solid for one sign of
active forcing, and the instability of the orientationally ordered phase in
momentum-conserved systems for large active forcing irrespective of its sign.
