Detectives have published CCTV pictures of the gang they suspect left a young Brighton musician with a broken jaw.
They have urged the men to turn themselves in before they are arrested while the victim’s father has offered a reward.
One of the men attacked Miles Ward, 23, shortly after he finished a gig in the centre of Brighton.
He was in Black Lion Street talking to a busker outside the Thistle hotel when the group came past.
There were about half a dozen of them and one of them kicked over the busker’s cup of change.
Mr Ward, a pianist and singer, asked him to help pick up the change.
Instead the man punched Mr Ward in the face, breaking his jaw in two places.
He was taken to the Royal Sussex County Hospital where he had surgery during which metal plates were inserted.
The men walked off up Black Lion Street after the attack which happened at about 11pm on Saturday (28 July).
Mr Ward’s father is Bob Ward, who fronts the Railing Stains, a Rolling Stones tribute band.
He said: “Obviously, I am sickened by this assault on my son but it also bothers me that someone who could attack at random like this could well do it again and the consequences could be worse.
“I love Brighton and it angers me that there’s someone out there who taints our city with violence of this kind.”
He hasn’t said how much the reward will be but it will be paid out for information leading to the arrest and conviction of the man who attacked his son.
The main suspect was described as a blond-haired white man in his early to mid-twenties, between 5ft 7in and 6ft tall. He was wearing a light-coloured shirt and jeans.
Almost two weeks after the attack Mr Ward remains in a great deal of pain.
Dectective Constable Caroline Ingold said: “It is going to be at least six months before Miles is able to function normally.
“This attack has had a particularly bad effect on him as he is a musician, plays piano and sings.
“He is studying at music college and is unable to take part in college or work now because he can’t move his mouth.”