Memory Increases When Merging and Playing Audio - ios

Question

I'm trying to merge multiple pieces of audio into one simultaneous sound and then play it. I can merge and play, but my app's memory usage keeps increasing over time.
Looking online, it seems like there's ARC/memory issues with AVPlayer.
I've added all relevant code below for setting up the files, merging them and then playing them.
Setting up sound files
- (void) setUpSoundFiles {
AVURLAsset *songAsset = nil;
AVAssetTrack *sourceAudioTrack = nil;
for (int i = 0; i < numberOfSoundsToMerge; i++){
NSURL *url = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:[#(i) stringValue] ofType:#"mp3"]];
songAsset = [AVURLAsset URLAssetWithURL:url options:nil];
sourceAudioTrack = [[songAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
[songTracks insertObject:sourceAudioTrack atIndex:i];
[songAssets insertObject:[AVURLAsset URLAssetWithURL:url options:nil] atIndex:i];
//[sourceAudioTrack.asset cancelLoading];
}
}
Merging Sound Files
- (void) mergeAudio: (AVMutableComposition *)composition{
for(int i = 0; i < numberOfSoundsToMerge; i++) {
AVMutableCompositionTrack *track = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
NSError *error = nil;
BOOL ok = NO;
CMTime startTime = CMTimeMakeWithSeconds(0, 1);
CMTime trackDuration = ((AVURLAsset *)[songAssets objectAtIndex:i]).duration;
CMTimeRange tRange = CMTimeRangeMake(startTime, trackDuration);
//Set Volume
AVMutableAudioMixInputParameters *trackMix = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:track];
[trackMix setVolume:0.8f atTime:startTime];
[audioMixParams addObject:trackMix];
//Insert audio into track
ok = [track insertTimeRange:tRange ofTrack:(AVAssetTrack *)[songTracks objectAtIndex:i] atTime:CMTimeMake(0, 1) error:&error];
[((AVAssetTrack *)[songTracks objectAtIndex:i]).asset cancelLoading];
}
}
Playing Sound Files
- (void) playSounds {
AVMutableComposition *composition = [AVMutableComposition composition];
audioMixParams = [[NSMutableArray alloc] initWithObjects:nil];
[self mergeAudio:composition];
AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];
audioMix.inputParameters = [NSArray arrayWithArray:audioMixParams];
AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:composition];
AVPlayer *player = [[AVPlayer alloc] initWithPlayerItem:playerItem];
[playerItem setAudioMix:audioMix];
[player play]; }