Watch Taylor Swift's emotional performance of 'New Year's Day' on 'Tonight Show'

Taylor Swifthelped bring some joy to a grieving Jimmy Fallonwhen she made an unscheduled appearance on his late night show.

Swift, whose new album Reputation dropped last Friday and is charging to the chart summit in the U.S., U.K. and in markets around the globe, stopped by the Tonight Show studios Monday evening to dish out some music therapy: a performance of "New Year's Day."

The talk show host canceled all of last week's tapings following the death of his mother, Gloria Fallon, and returned Monday night, still visibly shaken from his loss. Holding back tears, Fallon at one point recounted a childhood memory of his mom squeezing his hand three times to say "I love you."

Tonight Show writer and producer Mike DiCenzo took to Twitter for some background on Swift’s performance and the emotions she wrought. “She was not scheduled to do our show today. But we wanted something special for this first show back, so we asked her on a complete whim, since she had been in town doing SNL. She said yes with zero hesitation,” he explained.

See recent photos of Taylor Swift:

While singing "New Year's Day,” Swift delivered a lyric which paraphrases Fallon’s tender story -- "Squeeze my hand three times in the back of the taxi." DeCenzo and his fellow Tonight Show crew were in bits. "I nearly gasped. Tears. I think everyone in the audience started sobbing. I could see Jimmy silhouetted at his desk dabbing his eyes with a tissue. We all lost it. It was a beautiful coincidence in a beautiful performance," he wrote.

Fallon and Swift’s hug at the end was "100% real emotion. Whatever you think of Taylor, she did something beautiful for Jimmy and our show today, and we're forever grateful,” said DiCenzo.

Watch Jimmy Fallon's tribute to his mother below: