Can someone explain to me the appeal of The Grateful Dead's music?

One interesting thing about the band is its place in the in the counter culture; Tom Wolfe’s Electric Kool Aid Acid Test chronicles this. Jerry Garcia had worked as a security guard in a mental hospital at the same time as Ken Kesey, the author of One Flew Over the Cuckoo’s Nest. Kesey and his group of friends, The Merry Pranksters (which included Neal Cassady, the basis for Dean Moriarity in Kerouac’s On the Road) used to throw parties that they called Acid Tests, at which The Warlocks (who would soon be renamed The Grateful Dead) would perform; at these parties, the music was part of the scene, not the scene itself, which was mostly about taking LSD and tripping balls.