Ever watched Whose Line Is It Anyway? ...I really hope so. Because that's exactly what this is, only for a forum.
1. First person sings a line
2. Next person sings a line
3. Next person sings a line
4. Final person sings a line that ends by rhyming with the ending of line 2.
5. Repeat 1-5.
Pretty simple. Typically, the 1st nd 3rd lines have 7 syllables while the 2nd and 4th have 5, but that's not always the case. Person who begins the song will select a theme. Each song is 32 lines. (16 rounds) It doesn't have to be the same 4 people for each song. Just go once per round (every 4 lines)
Need some examples of what I mean? I'll start us off with... the Fire Emblem Awakening Irish Drinking song!
Ohhhh, aye-dee-di-dee-di-dee-di-dee-di-dee-di-dee-di!
I just defeated endgame~