There are hundreds of tribute bands performing the music of the Beatles, Rolling Stones, AC/DC, Led Zeppelin, U2, and other monsters of rock. But Crosby, Stills, Nash, & Young?
Next to none.
A band dedicated to tributing CSNY is unheard of due to the difficulty in replicating the 3- and 4-part vocal harmonies that made the group international superstars.
Marrakesh Express excels at reproducing CSNY's complex songs and cascading, layered harmonies.