Phil Lesh Didn’t Hold Songs Down. He Lifted Them Higher.

Some rock bassists make it their job to hold down the bottom of a song: to hone parts that crisply but unobtrusively stake out a harmonic and rhythmic foundation, that are felt as much as heard. Phil Lesh, a founding member of the Grateful Dead who died on Friday at 84, wasn’t one of them. Instead, Lesh’s playing carried songs aloft.

In the telepathic tangle of the Grateful Dead’s arrangements — never played the same way twice — Lesh’s bass lines hopped and bubbled and constantly conversed with the guitars of Jerry Garcia and Bob Weir. His tone was rounded and unassertive while he eased his way into the counterpoint, almost as if he were thinking aloud. Lesh’s playing was essential to the Dead’s particular gravity-defying lilt, sharing a collective mode of rock momentum that was teasing and probing, never bluntly coercive.

Lesh wasn’t a rock-and-roller by training or inclination. His 2005 memoir, “Searching for the Sound,” notes that his first instruments were violin and trumpet, that he soaked up classical music and big-band jazz, that he studied music theory and composition and drew life-changing inspirations from John Coltrane and Charles Ives. He and Tom Constanten, the Dead’s early keyboardist, were the band’s avant-garde contingent, a key aspect of the Dead’s ever-evolving improvisational fusion.

For all their free-form interludes, the Dead’s songs had clear landmarks and structures — some of them far trickier than the band’s nimble performances would let on. Lesh could stick to a riff, as he dutifully did in the intro to “Touch of Grey,” the Dead’s only Top 10 (and only Top 40) single. But when the verse arrived, he was footloose again: nudging, scurrying, syncopating from below. His bass lines held hints of Bach, jazz, bluegrass, blues, Latin music and far more, as he sought out new interstices each time through a song.