code: function Header(fileType, trackCount, ticksPerBeat) {
      this._fileType = fileType || Header.FILE_TYPE.SYNC_TRACKS;
      this._trackCount = trackCount || 0;
      this._ticksPerBeat = ticksPerBeat || 120;
  }
docs: Construct a new Header
  
  @class Header
  @classdesc A Standard MIDI File's header (contains various metadata)
  
  @param {module:midijs/lib/file/header~Header.FILE_TYPE}
  fileType File type
  @param {number} trackCount Amount of tracks in the file
  @param {number} ticksPerBeat Beats rate in ticks per beat