He was 95 and passed from cancer, his son said.
Jones kept working on the piece with Schmidt that was originally devised with Robb.
The play used a narrator and minimalist staging, both unusual steps away from the formula of a bigBroadwaymusical.
The initial reviews were mixed, although some critics raved.
Jones and Schmidt went on to collaborate on other shows.
He also wrote the book and lyrics for I Do!
Each of those shows earned the men Tony Award nominations.
Ed Amess version of My Cup Runneth Over, a song from I Do!
I Do!, peaked at No.
8 on the Billboard Hot 100 in 1967 and received Grammy Award nominations.
Of course, nothing compared to The Fantasticks.
The show revived in 2006 in Manhattan and ran for more than 4,300 performances.
Joness first marriage, to Eleanor Wright, ended in divorce.
His second marriage was to the choreographer Janet Watson, who died in 2016.
Michael Jones and another son from that marriage, Sam, survive him.