again i say function speaks most here. to any of you have not had a chance to listen to the her playing it, go here:
http://www.showmethat.com/index.php?pr=DVD_CLIPS and click view video under cassandra o'neil... the change happens as she's going into the chorus the first time.
forget about letters and numbers just for a second. when she hits that chord, listen to where your ear is expecting her to go. im pretty sure when she hit that g minor chord right afterward, it was no surprise to you. theoretically, that makes sense because iii follows ii (in an earlier post i defined this chord as ii half diminished 7 in first inversion). however, iii does not follow IV (theoretical guidelines state: down a fifth, down a third, up a second). so if it was some kind of chord with Ab as its root, following the guidelines, the chord following would be VII, ii, or V.
it is important to learn the letters and the numbers, but these things only
define what you are listening to. the aural part of music is by far the most important. learn to trust your ear, while learning the system of theory, so that you can define what it is that you've already learned.