What's the idea, then?

We have thought of asking participants to prepare a song by themselves, among a number of suggestions, and then to have ONE SONG for all of us to sing along together!
We will have a number of songs to share a meeting: there could be solos, duets, choirs, etc.
Before each performance, we will refer to the author, the song, the country where the author is from. We will also focus on some vocabulary to help comprehension.
After the performances, we will give the singers a score (from 1-5) based on:
1. Courage to sing!
2. Intonation,
3. Articulation,
4. Foreign accent-reduction
5. Audience encouraging
6. Enthusiasm when singing the song,