Here is an idea, for a different approach to the song challenge idea.
The organiser chooses a theme, the rules and a limited time period, as usual.
At the end of the time period, the organiser finalises the list of entries based on what has been submitted, and is entitled to see Reason files at request if needed to verify participants have followed the rules.
A poll is then run where people can vote for the tracks they like. The winner has the most votes. People can vote for as many tracks as they like, so that reduces chance of some entries getting no votes and people being disappointed.
No prize other than the kudos