One of the tracks on FTD volume 4, the instrumental "Fire Down Below" originally the track contained the vocals of Sherril Nielsen's as a guide (which would give away the whole melody and the lyrics) but were removed for this release. The reason was that now that writer Jerry Scheff can still use the song for one of his own projects.
However, Jerry seems to have told that if they release this song, or even the track, that he will sue them.
The biggest surprise is a couple of seconds of the great finale of "America The Beautiful" from these sessions (rumours that this track existed, already circulated among fans in 1976!), which is all they have of this song.