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Forgive my ignorance but what do you mean by 'encore shows'?
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These were authorized live soundboard recordings that were sold by themusic.com, by arrangement with the artist.
There were eight Gabriel tours, from 2003 to 2014 where (I believe) every show was recorded and sold as part of this Encore series.
I bought several of them over that stretch. They were a nice quality-sounding alternative to bootlegs
In addition to Gabriel, there was an Encore series during Genesis 2007 tour.
Other bands that did this in 2000s were The Who and Duran Duran.
I've never seen these recordings commercially available other than through themusic.com, so I would think nugs.net would have to obtain or purchase the rights to these recordings from that third party.