I keep all my music (in my Note II, but this has been the same in my previous Android phones) in a folder called Music in my SD card. I use Windows Explorer to create it, with USB cord connected to my computer and phone set to USB Debug (a little harder to find in my latest phone, but it's there). Also, created playlists on my computer with Windows Media Player, and JRiver Media Player. WMP creates .wpl files. JRMP exports to .m3u format. I keep these in a subdirectory called "playlist" in my Music directory on my phone.
Android scans the SD card on startup, finds these playlist files, matches them up with the songs in my phone. Even though the playlist directory locations in the .wpl and .m3u files are for my computer -- somehow Android can find them in my phone anyway.
(Digression ... if I move music to a different directory or drive in my computer, both WMP and JRMP are unable to use the playlist files. If Android can find the songs wherever they are, WMP and JRMP should have that option too.)
Note that I use MixZing as my music player, but it doesn't handle this playlist issue ... that's handled by Android (standard music player, I guess).
Odd note ... it seems to be important that the subdirectory for my playlist files be "playlist" (singular). I tried having the subdirectory be called "My Playlists" like Windows 7 created it, only to have Android decide that meant I wanted 2 playlists for each of my playlist files. Really. No idea why. I deleted all of those (double) playlists (using MixZing), transferred all the playlist files to "playlist", rebooted phone, and now I have one, and only one, playlist for each of the playlist files. This is something I figured out a couple of phones ago, and don't remember where I got it.
I've tried other programs which are supposed to automate this process, like Double Twist (Doubletwist?) and they drove me crazy. I like the simplicity of drag & drop (well, simplicity, now that I figured it out).
