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Does Bruce Hornsby join the band, Grateful Dead?
In 1988, Bruce Hornsby first appeared on stage with the Grateful Dead, a recurring collaboration that continued until the band's dissolution
When did Bruce Hornsby join the Grateful Dead?
In 1988, Bruce Hornsby first appeared on stage with the Grateful Dead, a recurring collaboration that continued until the band's dissolution

Question: Was the group already formed when he joined?
Self-contained rewrite: Was the Grateful Dead already formed when Bruce Hornsby joined?