I’m a little slow on the uptake,  and just realized Yom Kippur starts at sundown tonight and runs through sundown Sat night!  Also known as “the day of atonement”,  YK is one of the most important days on the Jewish calendar.  I know there are plenty of songs that will be a good fit,  I just haven’t started looking for them.  If you have one you think would be perfect Saturday afternoon,  let me know.

Disc 1 of the collection People Take Warning! (Tompkins Square Records) has Josef Rosenblatt singing a memorial for the Titanic victims in Hebrew. It doesn’t sound all that folky, but is otherwise very appropriate and could be coupled with another song on the same theme (When that great ship went down, etc.)

This isn’t a song recommendation, I’m afraid, but your question led me to this page about Jewish bluegrass music. Thought it was interesting enough to share - http://www.smithsonianmag.com/arts-culture/Jewish-Bluegrass.html.

This is useful: http://nwfolk.com/songlists/high_holidays.html

Nothing much yet but you could keep an eye on: Jewish Holiday Songs thread on mudcat.org.

Tzena Tzena Tzena was made popular in the US by the Weavers but my favorite version of it is actually by African-American vocal duo Joe and Eddie.  Not directly related to Yom Kippur but a great rendition of a popular Jewish song by a totally under-heard Folk duo.

As I understand the observation, the faithful abstain from eating/drinking, sex, bathing, etc.  That’s a tough list to accommodate so perhaps songs of solidarity might be in order - blues for the lack of sex, bluegrass for the dangers of too much drink, bluegrass and old time to warn against the dangers of bathing… 

Adam