  This paper describes an enumeration of all words having a combinatoric
property called "rhythmic oddity property"named \emph{rop-words}.\ This
property was introduced by Simha Aron in the 1990s. The set of rop-words is not
a subset of the set of Lyndon words, but is very closed. We show that there is
a bijection between some necklaces and rop-words. This leads to a formula for
counting the rop-words of a given length. \textsc{Keywords:} Combinatoric on
words. Lyndon words. Rhythmic oddity. Music formalization
