'Get Together' Singer Jesse Colin Young's Cause of Death Revealed

Folk rock singer Jesse Colin Young died from a heart attack ... TMZ has learned.

According to the Aiken County Coroner's Office in South Carolina, the Youngbloods singer died from cardiac complications of atherosclerotic and hypertensive cardiovascular disease.

In the case report, obtained by TMZ, the coroner say Jesse died at 3:13 PM Sunday and the manner of death is classified as natural.

The docs also reveal Jesse died at Aiken Regional Medical Center.

As we first reported ... Jesse was at home on Sunday afternoon when paramedics were called to his residence and he was transported to a hospital, where he was pronounced dead.

He was famous for his time with the 1960s counterculture folk rock band the Youngbloods ... plus a long and successful solo career.

Jesse was 83 ... and the case report notes his body is now at a South Carolina funeral home.