If it was advertised and sold to you as a Blackstar show, then ya i think you have the right to be disappointed. Not that theres shit you can do about it...but i'd be disappointed to.
If its billed as Mos def with special guest talib, then i think its safe to assume they're only doing like 1-2 songs together if that.
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Ever wonder why you can see the whole width of this sentence but you still have to move your eyes to read it?