  In theoretical hadron physics mesons are a center of attention. Constructed
in a simpler way than baryons in the quark model, they still present a
considerable challenge if one aims at an understanding of all their aspects in
terms of quarks and gluons in the context of Quantum Chromodynamics, the
quantum field theory of the strong interaction. Complementary to (constituent-)
quark models, reductions of the Bethe-Salpeter equation, lattice QCD, and
effective field theories, the Dyson-Schwinger-equation approach has emerged as
a well-suited formalism for the covariant study of hadron properties. In
particular, radially excited mesons exhibit a sensitivity to long-range
strong-interaction physics. This sensitivity has recently been studied with the
help of the Bethe-Salpeter equation. Here these studies are reviewed and
continued together with an account of possible future developments.
