Dwayne Vincent, 26, whose stage name is Megaman, one of the founding members of the south London rap collective, was said to have encouraged Carl Morgan to open fire.
It was alleged that Mr Morgan, 24, shot Colin Scarlett three times just fours hours after they had had a fight.
The court was told that Mr Scarlett, 24, had fought after Mr Morgan assaulted his girlfriend, Elisha McFarlane, who had been Mr Morgan's girlfriend.
The men had gone to Mr Scarlett's home in two cars - one of them Mr Vincent's silver Golf, the prosecution alleged. Mr Vincent, of Barons Court, west London, had knocked on the door and Mr Scarlett chose not to open the door, Richard Horwell, for the prosecution said.
Mr Horwell said that once Mr Vincent had left, Mr Scarlett armed himself with a modified pistol that fired metal projectiles.
"Scarlett must have known Vincent was either armed or that Morgan was armed - his assumption was correct.
"There was a stand-off between him and some of his friends - with Morgan, Vincent and their supporters ... it seemed more reminiscent of the Wild West than south-west London.
Mr Horwell said that Vincent told Morgan, of Battersea, south London, to shoot Mr Scarlett on 6 November last year.
"This case is about humiliation, revenge and execution," Mr Horwell said. "Following the humiliation Morgan plotted his revenge.
"If Vincent's friend had been humiliated and beaten he had to step in to support him and to avenge him. Vincent told Morgan to shoot Scarlett. Vincent as a leader must have known what effect his words would have."
The court was told that Mr Morgan had a relationship with Mr Scarlett's girlfriend in the past. It had lasted for seven years and they had two children, aged four and two years.
They had separated a few years before, but he found it unacceptable that she sometimes stayed the night at Mr Scarlett's home.
The court also heard that earlier on the day of the alleged shooting, Mr Scarlett, accompanied by two other men, had beaten Mr Morgan outside his home, near to his children and in front of his ex-girlfriend.
Mr Vincent and Mr Morgan denied the charges. The trial continues.