I have been experimenting with the combination of music and chess this year.
Children are usually very excited when they play chess and the noise inevitably builds up from initial whispers to torrents of conversations. This has the obvious effect on concentration levels and leads to blunders.
Playing soothing music - not too loudly - as the children play their games is having a big impact on the problem. Further tests are required and will definitely follow over the remainder of the school year.