On the evidence of a door locked from the inside and information that, six years earlier, the singer had been diagnosed as a paranoid schizophrenic, police assumed suicide. Some of his family and friends, however, maintain that Hathaway's death was accidental; that his mood on the night of 13 January, 1979, when he'd recorded lead vocals to "Back Together Again", later to become the last of his successful duets with Flack, had been relatively upbeat. Whatever the truth, there's no doubt that the demise of Donny Hathaway at the age of 33 robbed the music world of one of its most naturally gifted performers.
Eric Mercury, co-writer and co-producer with Stevie Wonder of "You Are My Heaven", the other tune recorded by Donny on the fateful night, unhappily describes what had become a typical studio session for his disturbed friend.
"That album, what became Roberta Flack Featuring Donny Hathaway, was supposed to be duets all the way through. In the end, Donny contributed to only two songs. He was so sick he really shouldn't have been expected to do it. In the studio he'd been talking to us in one voice and then answering himself in another. Other times he'd sit down at the piano and play all these fantastic classical themes, stuff he'd written himself. We cut what we could during lucid periods. In the end, the nurse he had with him didn't ultimately save his life. My view is he should never have been left on his own."
Speaking publicly for the first time, Hathaway's widow, Eulaulah, herself a professional classical singer, admits that her former husband's condition had deteriorated to the point of danger: "He'd been diagnosed paranoid schizophrenic in 1973 and subsequently was hospitalised several times. Like most people who take daily medication, Donny began to think that, if he felt better, he could go it alone: he'd come off his medication and he'd end up getting worse.
"But at no point had he ever tried to harm himself. The point is, all New York hotel windows will come open and if you are neglectful enough to sit on such a ledge, you just might fall. Did he feel under pressure from the record company to do the album? Let's just say, if he was still up to it vocally, then..."
Donny Hathaway was born on 1 October, 1945, in Chicago, but largely brought up by his grandmother, Martha Crumwell, in a poor part of St Louis, Missouri. She was paraplegic but also a noted local gospel singer, and encouraged her charge's obvious musical talents through the church. It wasn't until Donny won a scholarship to Washington DC's Howard University that he encountered the "devil's music" that was jazz, soul and pop.
Seventies soul star Leroy Hutson, Donny's roommate for two years at Howard and writing partner on several of his most memorable songs (including his biggest solo hit, "The Ghetto"), remembers his friend as both an overwhelming talent and a social innocent abroad: "I recall one time, maybe a month into us being roommates, he came home when I was playing Miles Davis' Porgy & Bess album, the one with the elaborate arrangements by Gil Evans. He sat on the couch and listened for a while. Then he began moving the needle around from cut to cut. After that he sat down at the keyboard and rearranged the whole thing as it was playing. He stretched the chords and made it all his own. It was an incredible experience.
"But he found himself living life at so fast a pace, he couldn't really handle it. He became prone to making, let's say, unwise decisions - hangin' with the people that could do him no good, getting himself into deals that could and did hurt him. The contrast between his upbringing and what he found in DC and the record business was something he never came to terms with."
Hutson and Hathaway both sang for The Mayfield Singers, a vocal group put together by Impressions leader and Chicagoan soul power-mover, Curtis Mayfield. After two years of straight As, Donny was seduced into joining Mayfield's new label, Curtom, as in-house arranger and writer for acts like The Impressions, The Five Stairsteps and Holly Maxwell. Even the man who created Superfly was surprised by what he'd signed: "To see him there in the studio at about 21 years of age, directing all these real big session guys like he'd been doing it for years, was a tremendous sight to see. But he always believed in himself. He wasn't conceited about it, but he knew he could do anything these guys could do, and almost certainly better. I'd have loved to sign him as an artist, but it wasn't to be."
Instead, in 1969, Hathaway joined Jerry Wexler and Ahmet Ertegun's Atlantic Records. In 1970, "The Ghetto" was released, featuring both his wife, Eulaulah, and crying eight-month-old daughter, Laylah: it was a huge R&B hit. The album which followed, Everything Is Everything, attracted huge acclaim for its merging of classical, jazz and gospel styles.
Then, in 1972, Wexler's suggestion that Donny team up with another of his old college friends, Roberta Flack, for an album of duets, paid commercial dividends. A single, the almost cocktail lounge-smooth "Where Is The Love", was an international Top 10 pop hit, rocketing the Roberta & Donny album to the top of the American album charts. It provided the platform for a slew of Hathaway solo releases throughout the rest of the year, including a superb live album, and his entry to the blaxploitation movie soundtrack archives, Come Back Charleston Blue, which Donny wrote, arranged and performed under the guidance of Quincy Jones. The stage was set for what many regard as Hathaway's masterwork, 1973's Extension Of A Man.
"As its title suggests," says Roberta Flack, "that album showed all the facets of Donny's talents. One of my favourite tracks by him is `Come Little Children'. It's basically a call'n'holler song, like the slaves in the fields would sing, and yet Donny made it 5/4 - not a rhythm you'd associate with Afro-Americans at all. He could combine the church and the secular like nobody else. I was just glad the record company didn't make him sit on top of some `rose garden' type strings, like they did to Sam Cooke."
She adds: "There was no end to what he would try. We had learned about writing a tone poem as the opening to a piece of music at college - but black people were not supposed to do that in their own music. So, in `I Love The Lord [He Heard My Cry]', he put it right there at the opening of the album, as first track. He wouldn't be contained."
Donny Hathaway: born 1 October, 1945; died 13 January, 1979