A fortysomething New Yorker got on a bus last month. A teen-ager got on afterward, sat next to him and noticed the Grateful Dead logo on his sandals. "Great concert last night," said the Kid. "I wanted to go again tonight, but I have an algebra test." "Yeah, me too," said his fellow rider, "but I've got two kids." The miracle of Jerry Garcia, really is that he managed to live so long and that in the process his music stitched together three generations. The rock geniuses of his time, the ones wedded as he was to excess - Jimi Hendrix, Janis Joplin, Jim Morrison - exist now only as icons, wistfully worshipped by kids born long after they died. But Mr. Garcia carried on, refusing to bend to slick packaging, playing long concerts in which the band members simply got up and gave everything they had, playing as long as they could stay on their feet, and taking the music wherever it led them. It was almost impossible to scalp tickets at Dead concerts; the Deadhead code led fans to give them away. Ironically, despite low ticket prices, unreliability, and no particular marketing strategy, the Grateful Dead turned into the highest-grossing rock band in history. What bound the generations of Deadheads together? It was undeniably the music, which reflected the unapologetic ethos of the times when the Dead were born. As long as there was a Dead tour on, the Summer of Love continued, despite the occasional bad trip when fans get hurt or violence broke out. Describing the music, rock critics talked of its eclectic mix, of Mr. Garcia's fluid unpretentious guitar work, of his direct, playful lyrics. What is often missed is the spiritual quality of Mr. Garcia's work. The Dead's soaring vocal harmonies, especially in the early 1970's evoked old-time hymn-singing, and the songs' subject matter - love, death, forgiveness, renewal - was universal and contemplative. "Attics of My Life" may be one of the most haunting rock anthems ever recorded, a song about the spiritual quest, and about grace. Those themes, along with the groups exuberant celebration of good times and earthly love, bound together a huge tribe of people, from children (Mr. Garcia had just released an album for kids) to grandparents and wrapped them all in tie-dyed T-shirts. Unlike so many other rock trends, the Deadhead phenomenon was welcoming and inclusive. The Dead did not snarl. Unkempt they may have been, but they were sweet, and the sweetness originated in Mr. Garcia's sunny nature. That sweetness, in the end, was probably what kept him alive. The excesses of the 60's felled many. To survive the drugs and the craziness one needed something more. Mr. Garcia kept himself going a long, long time on the sheer joy of sharing his music. Three generations are lucky he did.