Jules,

In the _Autobiography_  on page 61 of Neider's edition, Twain mentions a
string of minstrel songs, the first of which he also has Aunt Polly's young
child slave, Jim, sing in Adv. of TS:

"Buffalo Gals"
"Camptown Races"
"Old Dan Tucker"
"The Blue Juniata"
"Sweet Ellen Bayne"
"Nelly Bly"
"A Life on the Ocean Wave"
"The Larboard Watch"

I believe there are also songs mentioned in the Early Tales and Sketches,
but I can't recall specifics.  I know he talks about musicians there.

Also, in my dissertation, I wrote about Twain's use of songs in "Tom
Sawyer's Conspiracy."  Jim is thrown in jail after Tom's conspiracy goes
awry and leaves Jim on the scene with a real corpse.  In jail, he shows an
appalling tendency to break into song and dance a "breakdown" ("TSC" 234,
Ch. 9).

He sings "Ain't got long to stay here".  This might refer to the spiritual
"Steal Away," which repeats the line over and over within it.

It's reputed to be a song of the Underground Railroad, and is supposed to be
how some slaves signaled they were ready to escape and how some conductors
signaled that they were in the area.  This latter point is possibly
apocryphal; the source I read it in offered no support.  It seems plausible,
though.  The spirituals were often coded with references to heavenly freedom
that also meant breaking earthly bonds.

It might also refer to another spiritual collected by Eva Jessye called
"Ain't got long to stay heah" (published in _My Spirituals_ in 1927, but
remembered from her childhood in Coffeyville, Kansas).  It has different
words, but the same idea.  Both are lovely.  I have a copy of the sheet
music somewhere, but as I recall, the music is very different.

And finally, after the boys offer Jim an escape plan that makes the
"evasion" look like a walk in the park, Jim begins to sing "'Jinny git de
hoecake done,' and the gayest songs he knowed" ("TSC", 234, Ch. 9).  "Jinny"
is a minstrel tune by Joel Sweeney.  And then Jim does his dance.

Hope this helps.

Best,
Sharon