Nobody seems to have posted the CORRECT solution to this so here goes...
If you have your music in the correct file structure they will load up in manila music player very quickly and you wont get any sound effects in the library. I strongly recomend syncing your music with Doubletwist AT LEAST ONCE because then that puts everything into the correct folders for manila music player to read. Once you see how the folders are organized put your music in just like doubletwist has set the folders and manila player will sort everything properly and even if you have sound effects in your library which you shouldn't they'll be in their own folder and wont get in the way of your music.
Once you sycn your music with doubletwist sense music player will recognize the folder first and automatically load music from that folder.
The file structure goes like this
<Storage Card>
<Music>
<Artist>
<Album>
<*song name*>
So for example an Eminem song would be organized like this in folders on your storage card.
<Storage Card>
<Music>
<Eminem>
<Recovery>
<Cold Wind Blows.mp3>