Using background jobs to upload files
@file = File.new(params[:file])
      respond_to do |format|
      if @file.save
        format.html { redirect_to @file, notice: 'file was successfully uploaded.' }
        format.json { render json: @file, status: :created, location: @file }
        format.js
      else
        format.html { render action: "new" }
        format.json { render json: @file.errors, status: :unprocessable_entity }
        format.js
      end
    end
end

has_attached_file :file,
    :path => ":rails_root/public/system/:attachment/:id/:style/:normalized_file_file_name",
    :url => "/system/:attachment/:id/:style/:normalized_file_file_name"
  validates_attachment_content_type :file, :content_type => ['audio/mp3', 'audio/mpeg', 'audio/mid', 'audio/x-wav']

  Paperclip.interpolates :normalized_file_file_name do |attachment, style|
    attachment.instance.normalized_file_file_name
  end

  def normalized_mp3_file_name
    "#{self.mp3_file_name.gsub( /[^a-zA-Z0-9_.]/, ' ')}"
  end