Unfulfilled dreams ... Homeless man Donald Gould once had dreams of becoming a music teacher. Picture: YouTube/ Sly Dylan Source: Supplied

He was wearing an old, dirty singlet, and soot marks covered his arms. His hair was matted, and he was gaunt.

But when local homeless man, Donald Gould, sat in front of the recently installed public piano in the city of Sarasota, San Francisco, it was too beautiful to ignore.

Mesmerised by the music, Gould launched into American progressive rock groups Styx’s hit song, Come Sail Away, ­which charted at number 8 on the Billboard Hot 100 in 1977.

Stunned passers-by stopped to listen to the music, commenting on the complexity and richness of Gould's performance.

“Do you know how hard that piece is to play that?” one woman remarked, amazed.

“I do!” exclaims another.

The piano was donated to the area as part of the Sarasota Keys Piano Project, which aims to encourage creative expression in a public space.

Aroar Natasha recorded some of his performance, later uploading a video to Facebook where it has received almost two millions views since yesterday.

Speaking to local ABC media, Gould, 51, said he was just hoping to “make a couple dollars and get tips”.

“I didn’t expect it to jump out to this.”

Known around town as “Boone”, Gould sometimes treats passer-bys to a five-song set he learnt as a child, and calls his versions of classics such as Billy Joel’s “Piano Man” or Bach’s “Toccata”.

“I might not do the whole song complete as it was recorded originally, but I [know] enough to touch people out here -‘cause I’ve touched a lot of people, apparently,” Gould said.

Gould has not always been homeless. As a child, he cut his music teeth on the clarinet, eventually getting so good that he played the instrument for the US Marine Corps.

After his service, he returned home, intending to study music at Spring Arbor University, and one day become a teacher.

Heartbreaking ... “I was just hoping to make couple dollars and get tips”. Instead, he got fame. Picture: YouTube/ Sly Dylan Source: Supplied

But things went horribly wrong when he ran out of money three semesters short of graduation — and then lost his wife.

“They sat me down, and they told me what had happened, that my wife had passed away ... and I just lost it man,” Gould told ABC.

Next came substance abuse, which resulted in his three-year-old son being taken away by Social Services.

Eventually, Gould ended up in Suncoast, where he and fellow musical Paul Lonardro now play gigs.

Gould said that during his performances, children sometimes sit next to him, and for a moment, make him feel like the music teacher he so desperately wanted to be.

“I play the ‘Heart and Soul’ bass, and I say: ‘just hit the white keys, you can’t screw up’ ... It doesn’t matter how they play, if they play crappy or good, I always clap for them,” he said.

“I’m a nurturer, I’m a teacher.”

Since the viral video, a local bar has indicated they would be willing to consider Gould as a potential performer.

An estimated 55,000 female US veterans are now homeless.