I like the idea but a couple of thoughts to add to the stew:
I think we need to be inclusive, not everyone want to be in a competition all the time and be careful around the overhead/fatigue of monthly voting. So why not get the mods to have a monthly 'featured songs' with say 3 tunes, and then at the end of the year a vote on the 36?
In addition is you could then run a competition to do cover versions of the top 10 voted songs. I'm doing a cover song at the moment and its fascinating to try and interpret and give something different to an original and personally I'd be chuffed to bits if someone else wanted to cover a song of mine. It would also be fascinating to hear different interpretations given the diverse range we have in the forum.
Neil