Musicians have accused London 2012 organisers of asking acts to play for nothing despite an agreement that professionals would be paid.
Trombonist Steve Haynes said Locog had asked his brass band to play at the Olympic Park for no fee.
He said he thought being asked to play for no money undermined what he does.
Locog said it was not aware of any official approaches made to professional musicians asking them to perform for no payment.
But Mr Haynes, who has played in numerous West End musicals and TV programmes, said: "Initially we were delighted after receiving an email from someone at London 2012, asking us to play.
"But then, actually to find out that it was unpaid, I think this demeans what I've been training to do for 20 years."
In an email to Mr Haynes, Locog wrote: "I realise that no budget isn't ideal but then again it's not every day you get to perform at the Olympic village!"
An agreement between the Musicians Union and 2012 guarantees that all professional performers will be paid unless they are amateurs or headline acts happy to waive their fee.
Music agent JC Caddy said: "They've [Locog] been quite crafty about the way they're going about sourcing acts."
He said it was not right that musicians were not even being offered any travel expenses.
An email to Mr Caddy from Locog said: "They will be fed and watered while on site but I have a feeling we will struggle to get expenses together unfortunately."