First,it's a Robert Plant tour not a Led Zeppelin tour.
Second,I have found that most of the high pitched vocalists have lost that ability as they near the mid to late sixty age group.They just can't hit those high notes anymore,thus the restructuring of the material(think the Who at the super bowl).Not only that but I'm sure artists are sick of performing the same stuff for so many years.Just my opinion and you know what they say about opinions!!
Second,I have found that most of the high pitched vocalists have lost that ability as they near the mid to late sixty age group.They just can't hit those high notes anymore,thus the restructuring of the material(think the Who at the super bowl).Not only that but I'm sure artists are sick of performing the same stuff for so many years.Just my opinion and you know what they say about opinions!!