A documentary team that happened to be in the area caught the assailants on camera hurling abuse at their defenceless victim before one grabs, punches and kicks him.
One of the men, later named as Francis Muir, is shown swearing at the musician, known as Melo, and shouting: "You are taking the f****** p***. That's what you are doing. You are sitting here milking our country for thousands, ya f****** black b*******."
At one point Muir circles Melo menacingly, and the other assailant holds out his hand and tries to trick Melo into shaking it, but he sees through the ploy and urges: "Leave me alone."
The second man throws a punch but falls over as Melo dodges it and again pleads with them to leave him alone. He grabs the metal trolley he uses to move his equipment around and holds it up to the pair, saying: "Get away from me. Anymore and I will batter you both to the floor."
It is believed Melo was living in Glasgow after fleeing his home country Angola, which had been gripped by civil war, and first settling in Portugal. He is understood to have now left Scotland to live in England.
The incident lasted just over three minutes and took place in Glasgow's Sauchiehall Street. Police arrived at the scene and arrested the attackers.
Footage from the incident will be shown tonight on The Street, a BBC Scotland series following people working and at leisure in Glasgow's Sauchiehall Street.
Labour's shadow justice secretary Graeme Pearson, a former police chief, said it was the type of crime that occurs almost daily.
He said: "The documentary has caught the type of incident which, sadly, occurs probably most evenings somewhere in Scotland.
"It is symptomatic of a culture we need to tackle, in terms of racism and sectarianism - although at least those responsible in this instance were arrested.
"We need to come to terms with what is happening in our streets and change it.
"The reality is that people who belong to vulnerable groups, and people from different cultures, they know the truth - and they are victimised most weeks, if not daily."
Later in the programme viewers are told the assault brought back memories of the time Melo arrived in Glasgow 15 years earlier.
He said: "It was the second or third day. Someone said to me, ya f****** b******. It was a kid of 20 or so.
"Since then it has been like that every day."
Muir, 35, of Glasgow, was convicted of racially aggravated harassment and was jailed for four months in April 2012 for his part in the incident. His accomplice cannot be named for legal reasons.
l The Street is on BBC1 tonight at 10.35pm.