Rock-a-bye Baby
"Rock-a-bye Baby" was a 19th century lullaby composed on Earth. 

By the late-24th century the song had been revised to better suit the times: 

Rock-a-bye baby, in the spacedock,
When the core blows, the shuttle will rock,
When the hull breaks, the shuttle will fall,
And down will come baby, shuttle and all.

In 2378, The Doctor sang the 24th century variation of the song while he examined Seven of Nine's misaligned biradial clamp. After hearing the song, Seven asked whether he was "trying to soothe the infant, or traumatize her?" In response, The Doctor admitted that "the lyrics are rather grim, but it's the melody they respond to." 

The Doctor further revealed that "Rock-a-bye Baby" was one of twenty-nine songs he recorded as his baby shower gift for Tom Paris and B'Elanna Torres. Among the other songs he included in his recording were "a couple of Klingon lullabies," including his favorite: quong vaj Ocht or Sleep, Little Warrior. ()

Appendices

Background information 
The original lyrics for the song were:

Rock-a-bye baby on the treetop,
When the wind blows the cradle will rock,
When the bough breaks the cradle will fall,
And down will come baby, cradle and all.

The title of the undeveloped TOS episode "Rock-A-Bye Baby, Or Die!" was a reference to this song.

External link
 

fr:Rock-a-bye Baby
Earth musical compositions
Sleep