Jay-Z Leads Concert Fans in Singing 'Happy Birthday' to Beyonce

Jay-Z let his fans do the heavy lifting for Beyonce's birthday -- getting the crowd at his Made in America festival to to serenade her.

Bey was in the audience Sunday night in Philly when Jay-Z led everyone into "Happy Birthday" in honor of his wife's 36th ... which is actually on Monday.

As often happens ... fans sounded torn on which version of the song to sing -- traditional or Stevie Wonder. Beyonce smiled through it all with her Destiny's Child mate, Michelle Williams by her side.

Happy Beyday!