I'll put this here because it's the most active MM thread.
MM on the front page headlines of Yahoo.jp: "Why were Momusu able to do a comeback/break through again?"
http://dailynews.yahoo.co.jp/fc/enterta ... 1379722661The article is about the reason to WHY Morning Musume have come back and becoming popular again.
Of course they refer to the dances (starting from Help me!!) but they also touch on the singing abilities.
Supposedly Tsunku pushes the singing abilities in the group a lot because he wants to create a huge gap between other idols.
During recordings, unless the members appeal to him/the director that they want this or that part, they might not get it.
That is apparently a big/important thing in order to receive parts, and so to be able to do that (saying you want one part of course
won't make sure that you get it though) they also need to be good singers.
Also, the fact that despite popular members leaving, the group managed to go through their tougher times, is a huge factor.
While some members' leaving did have an impact on the fanbase, the fans didn't all go away and because of that it can easily be said that
Morning Musume are not relying on the popular members to stay relevant/have fans which is one of the bigger reasons to why Morning Musume are still doing so good. Another is that they bring in younger members constantly as well, which also is a big factor to how they can manage to keep being active and get new fans still.
According to the music critic and the idol critic that were interviewed for that article.