They have full members, affiliate members, and so on. They perform very frequently in different configurations, have fan clubs for individual band members (yes, the fans can keep track), and even votes for the most popular member. I will refrain from commenting on the music, but the performances involve singing and dancing.
AKB48 brings the idea of a band (if the name applies) as close to an organization as it can possibly get, and they are worth studying for that reason alone. The band is a franchise organization with a carefully cultivated brand, a strong marketing message, standardization of the product and even (because they perform in different configurations) the ability to deliver similar products (well, songs) in many places at once with good reliability. Remarkably, you could go to an AKB48 concert and know what kind of show to expect, even if you did not know who was going to deliver it. That is what good franchise organizations strive to accomplish (of course, I mean no comparison with franchises like McDonald’s on other dimensions).
The band members come in tiers depending on their experience and skills, and younger ones are carefully trained from being rather unpolished performers to reaching the first-tier AKB48 performer level. All this happens in full view of the fans, who often pick favorites among the younger members and follow their career as they go up the tiers of membership. AKB48 have even developed to the point of getting a fairly systematic career system that lets the most popular performers “graduate” into advertisement deals, television acting, and solo record contracts, while new ones enter the organization and start the same career path again. The franchise form of organization is known for its ability to deliver service reliably, in multiple locations, and over long time, and is also quite good at building up capabilities through experience. As a result, we often eat in franchises or get other services done there such as photocopying and haircuts, but even I had not anticipated seeing a franchise band.
Kenneth Maxwell. 2012. AKB48: World Domination, Phase II? Wall Street Journal Asia, April 4.