  We present the results of a covariant constituent quark model, based on the
Bethe-Salpeter equation, where confinement is implemented by a string like
linear potential explaining the Regge trajectories. An instanton induced quark
force explains not only the splitting and mixing of pseudoscalar mesons, but
suggest that such effects are also present in the scalar spectrum and in a
violation of the OZI rule in the decays of scalar particles into pseudoscalars.
We demonstrate that a covariant treatment that takes into account the
relativistic components in the amplitudes is of utmost importance when
describing properties of deeply bound states and/or processes at higher
momentum transfer.
