Milonga is a musical genre that originated in the Río de la Plata areas of Argentina and Uruguay. It was very popular in the 1870s. It was derived from an earlier style of singing known as the payada de contrapunto. The song was set to a lively 2
4 tempo, as are most milongas.
"Milonga is an excited habanera." The original habanera divided into four pulses, in a standard two-four where every note was stressed. In becoming milonga, though, all four notes turned strong, as tempo was doubled. The strength of the first beat weakened the fourth giving an almost waltz-like feel to milonga: one-two-three(four), one-two-three(four).Habanera is a slower, more explicit sounding one, two, three-four. At least one modern tango pianist believes the polka influenced the speeding up of the milonga.
Milonga has a syncopated beat, consisting of 8 beats with accents on the 1st (sometimes also 2nd), 4th, 5th, and 7th beats.
 2 3 4  6 7 8
 2 3   6  8, sometimes also   3   6  8
 2 3  5 6  8
Over time, dance steps and other musical influences were added, eventually giving rise to the tango.
By the 1890s musicians were writing in a structured form that was something more than thinly disguised milongas or tangos andaluces, and would later become the fully developed tango.