To know how it works exactly, read the thread. I tried to be as clear as possible.
I won't rotate modes after each song, but after each match. After a team wins a set (of 4 points with 2 more points than the opponent (4-2 for example), or 5 points with more than 2 points than the opponent (5-3 for example), or 5 points with 1 more point than the opponent after a tiebreaker (5-4 for example)) the next match for the next set will be another mode.
The mode order could be like this :
1st match (I'm talking about match, with serveral maps played in it, not just one) : Osu => first team who wins this, wins 1 set (by having won 4 points (see above))
2nd match : Taiko
3rd match : CTB
4rd match : Mania
If there are no winner, we'll continue until we have a winner
5th match : Osu
6th match : Taiko
7th match : CTB
8th match : Mania
At this point, if there's no winner, we'll do a tiebraker.
9th match (tiebreaker) : CTB
The order I gave you is an example. The mode order and the tiebreaker match will be randomly chosen and given with the mappools.
Was I clear enough ?