  Fractional quantum Hall liquids exhibit a rich set of excitations, the
lowest-energy of which are the magnetorotons with dispersion minima at a finite
momentum. We propose a theory of the magnetorotons on the quantum Hall plateaux
near half filling, namely, at filling fractions $\nu=N/(2N+1)$ at large $N$.
The theory involves an infinite number of bosonic fields arising from
bosonizing the fluctuations of the shape of the composite Fermi surface. At
zero momentum there are $O(N)$ neutral excitations, each carrying a
well-defined spin that runs integer values $2,3,\ldots$. The mixing of modes at
nonzero momentum $q$ leads to the characteristic bending down of the lowest
excitation and the appearance of the magnetoroton minima. A purely algebraic
argument shows that the magnetoroton minima are located at
$q\ell_B=z_i/(2N+1)$, where $\ell_B$ is the magnetic length and $z_i$ are the
zeros of the Bessel function $J_1$, independent of the microscopic details. We
argue that these minima are universal features of any two-dimensional Fermi
surface coupled to a gauge field in a small background magnetic field.
