I am trying to play music in my application. The music works fine but after switching viewControllers and returning to the main menu, my music plays again! It means several
Its seems you are developing game (from your function name After viewLoad (ScoreView). ;) )
Well, According to me, AvAudioplayer is not Good Option if you want to implement with Game.
Use cocosdenshion, Download the latest cocos2d folder, find the these 9 files, put it in your resource folder,

And You are done.. !!!
#import "SimpleAudioEngine.h" // wherever you want to call in head part of the file.
Step1 call short file.!
[[SimpleAudioEngine sharedEngine] playEffect:@"blast.mp3"];
step2 call background loop.
[[SimpleAudioEngine sharedEngine] playBackgroundMusic:@"background.mp3" loop:YES];
NOTE: There are list of available function http://www.cocos2d-iphone.org/api-ref/0.99.5/interface_simple_audio_engine.html , Its very easy and simple !
Whole implementation will take, 20 minutes max !