Conversation so far:
when did Bruce Hornsby join Grateful Dead?
from 1988.
How did he get involved?
he joined the band as a special guest and played accordion or synthesizer.
How long did he play with them?
until Jerry Garcia's death in 1995.
Who invited him to join the band?
CANNOTANSWER.

Question: Did the fans like him?
Self-contained rewrite: Did the fan of the Grateful Dead like Bruce Hornsby?