  The recent experimental results on the spectrum of highly excited light
nonstrange mesons are known to reveal a high degree of degeneracy among
different groups of states. We revise some suggestions about the nature of the
phenomenon and put the relevant ideas into the final shape. The full group of
approximate mass degeneracies is argued to be $SU(2)_f\times I\times O(4)$,
where $I$ is the degeneracy of isosinglets and isotriplets and O(4) is the
degeneracy group of the relativistic hydrogen atom. We discuss the dynamical
origin and consequences of considered symmetry with a special emphasis on
distinctions of this symmetry from the so-called chiral symmetry restoration
scenario.
