Hi,
@Noel, thanks; I've sent you the file.

@John--I have three different Midi buttons to choose from under Options, Pref: Midi File; Midi Drive; and Midi options. Which one will help answer. Remember, it does play correctly the first time through so I'm not sure how the midi options would affect it, but I don't really understand how the midi thing works.

I don't seem to have a "generate" button on my version (2007) but I think this is the same as the "play" button on my version. The problem occurs whether I use the play button or the replay button. First time I play the backup after opening BIAB it works perfectly for the 3 choruses I've set up. it reaches the end, and whether I hit Play or Replace, half the instruments drop out. Does this when I rename the file, too. And it seems to do it with other files, though I've only checked a few.

Thanks very much to both of you for responding. I haven't posted here for a while but I'm determined to get my BIAB chops up.