Swift | AVPlayer, load and play multiple audio files with one player

multiFilePlayer.swift

//Pass urls to files you want to play in one compossition, 
//works with any file recognised as AVAsset and containing audio tracks, 
//!!only first track in file will be played!! 

func loadFiles(filesURL: [URL]) async throws -> AVPlayer{
  //Initialize Mutable composition
  let composition: AVMutableComposition = .init()
  for file in filesURL{
            
    //Add new Composition track for new file
            
    guard let compositionAudioTrack: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: .audio,
                                                                                             preferredTrackID: CMPersistentTrackID()) else{          
      throw NSError(domain: "Can't create audio track composition", code: 100)            
    }
            
          
    //Create asset with url to file
            
    let asset = AVAsset(url: file)
            
         
    //Load audio tracks from file
           
    let track = try await asset.loadTracks(withMediaType: .audio)
            
           
    guard !track.isEmpty else{
         
      throw NSError(domain: "File \"\(file.lastPathComponent)\" doesn't contain audio tracks ", code: 100)
        
    }
         
    // create audio track
          
    guard let audio = track.first else{
        
      throw NSError(domain: "Can't extract audio track from tracks extracted from \(file.lastPathComponent)", code: 100)
         
    }
            
    // create time range
    let timeRange: CMTimeRange = .init(start: CMTimeMake(value: 0, timescale: 600),
                                       duration: try await audio.load(.timeRange).duration){
            // Set position you want track to be inserted at in "at" parameter(seconds)
            try compositionAudioTrack.insertTimeRange(timeRange,
                                                      of: audio,
                                                      at: CMTime(value: 0, timescale: 600))
        }
  }
  
  //Create PlayerItem to host prepared compositon
  let playerItem: AVPlayerItem = .init(asset: composition)
                
  //Create player with playerItem
  let player: AVPlayer = .init(playerItem: playerItem)
  
  //Return configuredPlayer
  return player      
}

Not perfect, I'll add AudioMix bit later to configure volume, pan etc. later