While Patti has a point about Hair (I saw it in the Park originally and understood what was going on then again a few weeks ago on Broadway where it was utterly unintelligible - and I'm 25) she may have missed the mark on Cirque du Soleil.
If her point is that only musicals should be in Radio City, that's one thing (and actually a rather invalid point considering she has been quoted as complaining that Radio City "swallowing up" musical performers thus why she doesn't like the TONYs to be held there) but the thing is: Cirque du Soleil is not a musical. There is music and singers in every show but their visibility varies from show to show.
Alegria: The Singer in White is featured heavily and given her on Entr'acte scene:
http://youtu.be/nWfmy5Tojdc Quidam: The male singer is in with the band and not featured on stage whatsoever while the female singer (scene on the swing) is the protagonist of the story:
http://youtu.be/MdqqssM3TW8 Cirque is about the full package, the visual molding with the sounds and ambiance to create an experience. That is there explanation for why many of their albums are not extracted directly from the show: as its own entity, the music is not supposed to be consumed on its own. It is part of the total package therefore needs to be beefed up for album release.
Furthermore, Cirque at least has quiet moments along with the loud and death-defying moments whereas HAIR stayed at full decibel for almost the entire show.