Standalone DVD-Recorders usually set chapter marks every ten minutes for a program you would record from TV or other source. It sounds like the DVD you mention has not been mastered in a software program but was simply recorded as is on such a DVD standalone recorder.
I am surprised to hear you can buy this concert on DVD though. A friend from UK once send me VHS tapes he had of a concert called Young and Fine and I thought it might be the same one, but it wasn't the 8:30 lineup but with Badrena and Acuna on percussions and drums, in Montreux 1976. I went through the hassle to digitize it and burn my own personal DVD from it, with menu and proper chapter marks. I think it is a really great concert from a fantastic period of the band.
Another maybe even greater concert I got recorded from TV actually does feature the 8:30 lineup and was recorded in Germany in 1978 for the popular German concert show Rockpalast. It is longer than the Young & Fine concert I know and contains a lot more songs. I am desperately hoping for this concert to be officially released on DVD some day, since currently many Rockpalast concerts are coming out on DVD, among them Mothers Finest, Level 42, etc. Look out for this one!
Mike, I realized the reversed melody line of Black Market on Zawinul's keyboard. Do you know more about the whys? I always wondered why he would do that?
Joni Mitchell's Shadow and Light concert is Pastorious at his best for sure. I just was so disappointed about the DVD when I realized that too many times the camera cuts or stays away from Jaco when it starts becoming interesting to see him. Aaargh! Of course the rest of the concert is great to see.
Hartmut