  The paper studies the vibrational modes of a slightly damped uniform chain,
with n masses coupled by elastic forces. It will be shown that, for certain
lengths of the chain, that is for certain values of n, the damping of one of
the masses at a specific position in the chain is able to constrain the
vibration of the system to oscillate at a specific frequency. The damped mass
turns out to be a node of the chain, subdividing it in two parts. This node can
be considered as the synchronization element of the two subchains. As a
consequence the oscillating system of n-masses is self-locking to the
synchronized frequency of its subchains.
