-(void)sessionDidEndPlayback:(id <SPSessionPlaybackProvider>)aSession

NSURL *trackURL = [NSURL URLWithString:self.trackURIField.text];
    [[SPSession sharedSession] trackForURL:trackURL callback:^(SPTrack *track)
    {

        if (track != nil)
        {

            haveObserver = YES;
            [musicPlayer stop];

            [SPAsyncLoading waitUntilLoaded:track timeout:kSPAsyncLoadingDefaultTimeout then:^(NSArray *tracks, NSArray *notLoadedTracks)
             {
                [self.playbackManager playTrack:track callback:^(NSError *error)
                 {

                    if (error)
                    {
                        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Cannot Play Track"
                                                                        message:[error localizedDescription]
                                                                       delegate:nil
                                                              cancelButtonTitle:@"OK"
                                                              otherButtonTitles:nil];
                        [alert show];
                    }
                    else
                    {
                        self.currentTrack = track;
                        [playAndPauseBtn setBackgroundImage:[UIImage imageNamed:@"pauseB.png"] forState:UIControlStateNormal];
                        [playAndPauseBtn2 setBackgroundImage:[UIImage imageNamed:@"pauseB.png"] forState:UIControlStateNormal];
                    }

                }];
            }];
        }
    }];