Executive Meddling: Several songs were purportedly chosen because Nintendo of America president Reggie Fils-Aime liked them. In addition, many rumors of a sequel exist purely based on the fact that Reggie was apparently quite fond of the game. Not that him getting us a sequel would be a bad thing.
In fact, it seems that "September" and a Jamiroquai track have to be in every music game Nintendo has some hand in, being as they are in EBA, Donkey Konga and... well, that's it.
"September" and "Material Girl" are also in Wii Music.
There's also this E3 trailer, which makes it a bit more similar to Ouendan.
Early press releases before the game came out listed Ricky Martin's "Livin' La Vida Loca" as one of the songs that would appear in the game; however, the song never made it to the final version. Interestingly, in the two-player song select menu, there's a blank spot at the end of the list that suggests that a level was indeed taken out late in development, lending credence to this possibility.