  The spectrum of excited isovector mesons is studied using a 32^3 x 256
anisotropic lattice with u,d quark masses set to give a pion mass near 240 MeV.
Results in the bosonic isovector nonstrange symmetry channels of zero total
momentum are presented using correlation matrices of unprecedented size. In
addition to spatially-extended single-meson operators, large numbers of
two-meson operators are used, involving a wide variety of light isovector,
isoscalar, and strange meson operators of varying relative momenta. All needed
Wick contractions are efficiently evaluated using a stochastic method of
treating the low-lying modes of quark propagation that exploits Laplacian
Heaviside quark-field smearing. Level identification is discussed.
