Beyonce's miscarriage inspired the "saddest song" she'd ever written, though the R&B superstar does not name the track in the forthcoming HBO documentary 'Life Is But A Dream.' The 31-year-old's husband Jay-Z briefly referenced the tragedy in Glory - a rap track recorded within days of Blue Ivy's birth on January 7, 2012 - though Beyonce has never discussed the loss.

However, in a surprising moment of honesty for the new documentary, the Grammy winner opened up, saying, "About two years ago, I was pregnant for the first time.And I heard the heartbeat, which was the most beautiful music I ever heard in my life." Of course, Beyonce and Jay-Z were overjoyed with the singer's first pregnancy, "I picked out names.I envisioned what my child would look like . . . I was feeling very maternal," she recalls. 

She suspected was something wrong in the early stages, revealing, "I flew back to New York to get my check up - and no heartbeat.Literally the week before I went to the doctor, everything was fine, but there was no heartbeat." Dealing with the heartache in the best way she knew how, Beyonce headed for the studio. "I went into the studio and wrote the saddest song I've ever written in my life.And it was actually the first song I wrote for my album. And it was the best form of therapy for me, because it was the saddest thing I've ever been through."

The singer - who performs during the half-time slot at the Super Bowl on Sunday (February 3, 2013) - admitted miming at President Obama's inauguration during a press conference on Thursday.

Watch Beyonce Launching Her Fragrance In New York: