My wife really likes her LG EnV phone. One of the features she uses heavily is the .mp3 playback, along with a pair of stereo Bluetooth headphones. But at first, I was going crazy because I couldn’t get songs to be reliably recognized when they were added to the my_music folder on the microSD card. I thought perhaps there wasn’t a proper “refresh” or “rebuild” of the music database when starting the phone up with the new files on it. After a lot of wasted time, I finally discovered that the problem was with the .mp3 filenames (or more accurately, with the EnV’s music player’s handling of .mp3 filenames). If the filenames contain more than about 30 characters, the phone simply will not recognize the files.
Note this is the filenames (as in MyArtist-MySong.mp3) that you see as you are copying files to the microSD card, NOT the ID3 tags that are read by most music players. There also seemed to be a potential problem with some odd characters. So bottom line: make sure the files you put on the microSD card have filenames with 30 characters or less, and only contains basic characters such as alphanumerics, underscore, hyphen, etc.