For an exhaustive account of both the (no-longer-extant) recording of
Twain's voice and all the beliefs concerning recordings of Twain, check
the Forum archives.  This subject comes up every couple of years, and I
know of no other single source as complete on the subject.

For voices other than Holbrook, try
http://etext.lib.virginia.edu/railton/onstage/voice.html
or link from the Robagoya-Juku English School site
http://www.asahi-net.or.jp/~XA3K-SOY/mt/goodsite.html

To get a copy of the recently "banned" Tom Sawyer play, I would suggest
trying to contact the teacher involved.  With a little research on
http://marktwain.about.com and the recent Forum archives, you should find
some very willing help.  It would be great if the play were performed
somewhere.  Keep us posted.

thanks and good luck, larry marshburne