Maybe originality is overrated. Today's biggest musical stars are like you--less concerned with writing something new, more interested in putting their own spin on old hits. A cappella groups epitomize this trend. But the technique only works if the performers (and in your case, re-recorders) are able to elevate the material. In movies terms, the same can be said about remakes and genre films. By those standards, Pitch Perfect has too many formulaic beats to risk being original, but it does a fine job remixing the standard musical comedy.
The bassline is as common as they come: a young, good-looking misfit comes to a new school and looks for a way to fit in. Her singing talents are hidden, because her first passion is to be a mixmaster (like you, Steve) who mashes up other the work of other artists. But at the behest of her father (what a twist!), she joins The Bellas. They're an all-female singing group that is a greatest hits mix-tape of high school outcast-types: there's the quiet Asian, the all-attitude African-American, the slutty sexpot, the uptight control freak, and the overweight comedic relief. Sounds familiar, but I guess that's the appeal of a remix.
There's a love story of course, and tension around keeping everyone together. But, like a good mash-up, it's the mixing of two divergent performances that make the film work. First, the understated approach of Anna Kendrick as the emotionally detached Bella, whose initial too-cool attitude rings true. She is contrasted with Fat Amy (Rebel Wilson), a bombastic Aussie who encourages said nickname so "twig bitches" don't say it behind her back. Where Bella embodies a withdrawn skepticism of the inherent cliches, Fat Amy embraces them unapologetically (and wins us over in the process). Kendrick plays her character straight, never coming across as pouty or petty, while Wilson proves she has an ear for comedy and is this year's breakout performer, following in the footsteps of Melissa McCarthy in Bridesmaids.
Aside from the deft humour, the musical performances are also infectiously in-tune. A vocal riff-off between the Treble Makers and rival groups blends musical styles into entertaining melodies, and it's during these interludes that the music is best able to influence the development of character. By the finale, most of the boxes have been checked, and we're able to sit back and enjoy the harmonies (plus at least one magic moment that sneaks itself into the story).
By and large, you gained my approval. But, Steve--would it really kill you to drop an unexpected beat on us every now and then? And no, that awkward, sequel-inspiring cut-off sentence at the end of the film doesn't count.