  We study numerically phonon modes of the classical one-dimensional
Frenkel-Kontorova chain, in the regime of pinned phase characterized by the
phonon gap and devil's staircase, as well as by a large number of states
(configurational excitations), which energy splitting from the ground state is
exponentially small. We demonstrate, these states behave like disorder media:
their phonon modes are {\it exponentially} localized, in contrast to the phonon
modes in the ground state, where phonons are {\it prelocalized} only.
  We demonstrate also, the phonon frequency spectrum of the ground state has an
hierarchical structure, a direct manifestation of hierarchical spatial
structure, found for the ground state of the FK chain in our recent work.
