On February 1 1986, John “Jellybean” Benitez’ Sidewalk Talk peaked at #18 on the Billboard Hot 100 in the USA.
The song was written by Madonna, arranged by Jellybean and Stephen Bray, produced by Jellybean and included the uncredited backing vocals of Catharine Buchanan and Madonna.
Today In Madonna History 
Sidewalk Talk-Yet another Madonna song that got away!
I believe this was released in 1985 not 1986 if memory serves correctly! 1985 was the year of the Madonna singles! And Madonna did the background vocals, while Madonna sang background!