Frère Jacques
"Frère Jacques" was a well-known children's song sung in the French language, usually used for basic melody training and practicing  music playing.

Jean-Luc Picard and the winners of the primary school science fair aboard the  sung this song while climbing up a turbolift shaft in 2368 in order to keep their attention off their predicament. () 

"Frère Jacques" was one of the first tunes that Captain Picard, as Kamin, learned to play on his Ressikan flute. ()

Picard (playing his Ressikan flute) and Nella Daren (playing her portable piano) performed a canon of "Frère Jacques" in Picard's quarters on the Enterprise-D in 2369. ()

External links 
History of "Frère Jacques"

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Earth musical compositions