It wouldn't have occurred to me to try this, but I'd already discovered that Emily's BlackBerry Pearl plays non-FairPlay iTunes AAC encoded tunes.
When I learned I could mass storage mount and charge my Nokia 6555b with a mini-USB cable and a (well made) Motorola mini-USB to micro-USB adapter the next test was to drop a podcast, an MP3 song and an AAC song into the mounted music folder. I then opened the music player, selected artists, and from the options menu chose "update library".
The All Songs list showed all three files  and they all played.
What's with music players and AAC? I don't remember anyone mentioning that players that were once entirely MP3 now all support AAC as well.
Unfortunately our HOSA headset adapters work only slightly better on this phone than on Emily's BlackBerry. If I don't press the 3.5mm terminal entirely in I get good stereo sound on my Bose QC IIs, but unbalanced stereo sound on a pair of Apple earbuds. If I do entirely engage the 3.5 mm connector I get mono sound. I'm tempted to try the Bose mobile communications kit.
The sad news is that the fairly crude music player doesn't support bookmarks, so it's not an adequate podcast player.
Even so, this is interesting enough to make me go ahead and buy another Sandisk 2GB media card, especially because I'm able to get my headphones to mostly work.
 It also showed the "." (dot) prefixed files that OS X creates on FAT formatted media, an annoying quirk of OS X that cannot be readily managed. There are ways to remove these, but I ignored them for this experiment.