The lives of Henry Grimes and Giuseppi Logan already felt like the stuff of legend long before they came to an end last week — just two days and one borough apart — from complications of the coronavirus.

Mr. Grimes, a bassist, and Mr. Logan, an alto saxophonist, were once the two biggest disappearing acts on the jazz avant-garde. Each shot to prominence in mid-1960s New York and then vanished, quickly and darkly, for decades. And then, in the new millennium, they both mounted triumphant returns.

Though they were never close friends or collaborators, their stories now feel cosmically linked. For a couple of artists whose music was about individual expressive freedom as well as interdependence, it is fitting that Mr. Grimes and Mr. Logan would now take their respective places in history side by side.

Both Mr. Logan and Mr. Grimes were born in 1935 in Philadelphia, a metropolis then flush with black musical innovation. Both passed through modern jazz groups (Mr. Logan with Earl Bostic; Mr. Grimes alongside a number of leading bandleaders, including Charles Mingus and Sonny Rollins) and the academy (Mr. Logan studied at the New England Conservatory; Mr. Grimes at Juilliard).

In New York, they became two of the primary voices in free jazz’s heady first generation, using sound to convey huge amounts of energy and agony. Embodying a kind of total sensitivity to the moment, pushing improvisation to its limits, Mr. Grimes and Mr. Logan contributed to a revolution in music that continues to ricochet, more than 50 years later, far beyond jazz.

Mr. Grimes eventually became a linchpin of free-improvising groups led by Cecil Taylor and Albert Ayler, and in 1965 he released a well-regarded album of his own, “The Call,” on the influential independent label ESP-Disk. Mr. Logan tended to lead his own groups, playing a range of instruments — from the Pakistani shehnai to the bass clarinet — and challenging his bandmates to upend their own roles.

Like Mr. Grimes, he released one studio album on ESP-Disk (“The Giuseppi Logan Quartet,” from 1964), following it a year later with a live recording, “More.” On both albums, harmony, rhythm and melody became agents of texture and suspense: Whether Mr. Logan is playing in apoplectic fits or in a long atonal smear, the radical open-endedness of each moment is palpable.

But by the late 1960s, Mr. Logan and Mr. Grimes — each seemingly at the height of his powers — had disappeared from the scene. For decades, each of them was a whisper in the back of jazz fans’ minds, a question it seemed wise to leave unanswered. Both struggled with mental illness, though maybe it’s more apt to say that each struggled to bring the world in tune with the music of his life.

Mr. Grimes had traveled to California to perform with the vocalists Jon Hendricks and Al Jarreau, but when his bass broke he sold it for a meager sum. Soon he was without either an instrument or money. For more than 30 years, he worked off and on as a janitor while battling bipolar disorder and scribbling dreamlike, often-beautiful poetry into notebooks. It was not until 2002 that a social worker and jazz devotee tracked him down in Los Angeles. The bassist William Parker had an instrument sent to him. Soon after, Mr. Grimes finally returned to New York, receiving a hero’s welcome at the 2003 Vision Festival.

Mr. Grimes had always had a bold, resounding bass sound, but upon his return, what those who played with him often noticed was his note choice. Even amid rancorous free improvisation, he still seemed able to select notes that were in perfect counterpoint to what surrounded him, such that they not only fit in but unlocked extra dimensions in the group sound.

The drummer Chad Taylor, who played hundreds of shows alongside Mr. Grimes in the Marc Ribot Trio, described the bassist’s note choices as “3-D.”

“He was always thinking of playing something against what you were playing,” Mr. Taylor said in a phone interview. “Against might not be the right word. Playing something different that would be complementary to what you’re playing.”

Mr. Grimes was a man of painfully few words, making it easy to misinterpret his silence as a consequence of age. But even as a young person he had been famously laconic; and as the decades advanced, he remained first and foremost committed to listening. In New York over the past 10-plus years, you were just as likely to find Mr. Grimes in the front row at a younger musician’s concert — eyes bright, body held upright, listening — as to see him onstage.

“He said very few words, but when he played, it was like kinetic radar waves,” Mr. Parker said. “He could listen; he could hear; he could push the music.”

“He was just very perceptive in his own way,” Mr. Parker added.

Mr. Logan was chattier by nature, and perhaps this became his saving grace. After bouncing for decades between Virginia and New York, cycling through homelessness and mental institutions — where he was often barred from playing music, only deepening his despair — Mr. Logan was at a music store in Manhattan one day, trying to buy a single reed for his saxophone, when he struck up a conversation with a young sales clerk.

That clerk was the trumpeter and multi-instrumentalist Matt Lavelle. When he discovering that this man was, indeed, the famous Giuseppi Logan, Mr. Lavelle became dedicated to bringing the saxophonist back into the music world. They recorded an album together, “The Giuseppi Logan Quintet” (2010), featuring a mix of Mr. Logan’s avant-garde compositions and the jazz standards he had by then been playing for years in public parks.

For Mr. Logan, even walking back into more standard repertoire was an expression of openness. As he had said years ago, describing his musical mission in a short documentary in the mid-1960s, “You have to get closer to your creator. Because that instills in the individual a love for everything, an unbiased heart.”

More than any happenstance similarities, it’s that omnivorousness that formed the crucial common bond between Mr. Logan and Mr. Grimes. They followed a hunger for listening into careers as performers, and found themselves pulled back into the fold, celebrated anew, by a community that wasn’t finished listening to them yet.