Ignore the entirely unrelated images. This is the only video I could find with the song by the original 1991 broadway cast. (Which, btw, is the cast I saw perform, way way back when.)
The song is 'I Heard Someone Crying' from the Secret Garden. The song takes place Mary's first night at her Uncle Archibald's house, she's unable to sleep because she can hear someone crying somewhere in the house, through the night, Mary and Archibald "mourn their losses" while the ghosts of their respective past (the ghosts of Mary's parents and others from India, and most importantly, the ghost of Archibald's wife Lily who died 10 years ago after the birth of their son.)
The original Broadway cast featured Daisy Eagan as Mary, Mandy Patinkin as Archibald Craven, and Rebecca Luker as Lily Craven. There are dozens of performances available on Youtube, mostly of amateur or high school productions, and although many of them have one cast member who is quite good - the Archibald Craven part seems comparatively easy, for instance - the Lily part features a lot of extremely high tones, which most of the singers struggled to hit.
Also, I honestly think you can't get better than the original cast here. Mary sounds a bit thin, but the strength of her personality and her stubborn will really come through, and I think it's very appropriate considering that so much of the musical is about these two children (Mary and Colin) caught in a world made by the adult's passion, obsession, love and loss. (Also, Daisy Eagan won a Tony for her role as Mary, at only 11 years old!) Mandy Patinkin has an amazing voice, which has been documented by people far more official than me, and I really think the song showcases it beautifully. Many other singers could sing this part, but the raw emotion he puts into it is amazing. And then there's Rebecca Luker. Her voice is so indescribably beautiful (her part in the background of around 2:16ish just gives me chills); she hits these crystalline highs effortlessly, and the haunting quality is perfect, as Lily is a ghost for entire musical (save the flashbacks).
I love the part that Archibald and Mary sing together, because I think that the way that the same words mean something very different to both of them - the widower lost in his grief and unable to move forward - and the girl trying to to find out what life means - really comes through.
( lyrics )