Two bandsmen played their instruments in the early hours of the morning as they crossed the Craigavon Bridge, a court has heard.
David Alan William Blair, of Rossdale, pleaded guilty to disorderly behaviour and indecent behaviour on December 8.
His co-accused, 23-year-old Steven Blair, of Garvagh Court, admitted disorderly behaviour on the same date.
Derry Magistrates Court heard that a group of men wearing band uniforms were playing their instruments as they made their way along London Street.
David Blair then stopped and could be seen on CCTV urinating behind a bin before coming out and doing up his trousers.
The men then made they way across Craigavon Bridge and onto Spencer Road still playing their instruments.
They were stopped by police and the Blairs were arrested for an illegal parade.
Defence solicitor Thomas Doherty told the court his clients had been at a band night and when they decided to walk home they continued playing their instruments.
District Judge Des Perry fined David Blair £25 for indecent behaviour.
Both defendants were then bound over in the sum of £200 to keep the peace for six months.
He warned them: ‘In your case keeping the peace means do not under any circumstances play your instruments other than in appropriate circumstances, processions or during properly constituted marches.
“Don’t form up a little band of troubadours in the middle of the night in Derry.”