from Psalm 137
By Bavel’s  waters
we sat and wept,
remembering the Temple. 
On Bavel’s willows
we hung our harps. 
For there, our captors demanded of us words of song.
They tormented us: “Be happy!
Sing us one of the Temple-songs.”
How can we sing G-d’s [Temple] songs
in a foreign  land? 
If I forget you, Temple, 
May my right hand be cut off!
May I die of thirst 
If I don’t remember you;
if I don’t place high the Temple 
as my greatest joy.
(There’s a musical round based on the King James version of this text:
A 3-part setting performed by Don Maclean on his 1971 album “American Pie” mistakenly attributed to the early American composer William Billings.
A 4-part setting by a 17th century composer named Phillip Hayes, which can be heard played on an instrument (not sung by voices) at: http://www.youtube.com/watch?v=jXxdhuVqaOc
Other recordings can be heard by googling “By the Waters of Babylon.”)
 “Bavel” is the Hebrew form of “Babylon”
 lit. “Tzion,” here referring specifically to the Temple, rather than to the entire land.
There’s a (now) well-known calypso-like song based on this psalm by Joseph Spence & the Pinder Family, collected in recording by Jody Stecher (who called it “the most beautiful song ever written,” perhaps without recognizing its basis in Tehillim/TaNaCh) in which “Zion” might refer to the entire land and be a metaphor for Africa, from which land so many were kidnapped to be slaves (i.e. were carried away; exiled). The latter meaning was certainly the case for Bob Marley’s Reggae/Rastafarian version of this song:
“The Rastafari way of life encompasses themes such as…the rejection of the degenerate society of materialism, oppression, and sensual pleasures, called Babylon. It proclaims Zion, as reference to Ethiopia, the original birthplace of humankind, and from the beginning of the way of life calls for repatriation to Zion, the Promised Land and Heaven on Earth.” (from Wikipedia)
 i.e. rather than perform Temple-music with them
 lit. a strange land
 How can we sing G-d’s songs in a foreign land?
On one level, this grief at the loss of everything familiar — particularly as it relates to worship — is poignant. The world as they knew it was gone.
On another level, though, G-d can be worshiped joyously anywhere, at any time. For example, we might use a siddur for formal prayer, especially in synagogue, but when necessary for us, we can speak with G-d anywhere, at any time, in the language most comfortable for us (e.g. Hitbodedut, as taught in Breslaver Hasidut).
We can, in effect, “sing G-d’s songs in a foreign land.” We are no less in G-d’s Presence among these “strangers” than in the Temple. These “strangers” are the very children of G- d for whom we are meant to be a light. To be a “light” here means to be a guide for them in becoming aware of G-d’s Presence, Justice and Goodness. We can only be a “light” to the extent that we sincerely recognize and affirm these things ourselves.
 lit. “Jerusalem,” meaning the Temple that had been there, not the entire city.
 lit. “May my tongue stick to my palate” — seems like an idiomatic way of saying “May I die of thirst…” — May I have no other joy in life if I can’t go to the Temple, my greatest joy…”