android - How to change frequency of audio file and save it as mp4 file on sdcard? -

i m trying make app user can record voice , can play voice in funny tone. talking tom application not that..he shd able share recorded sound file. m able record sound not able save file in funny tone..its getting saved in original tone. suggestions?

private void startrecording() {     mfilename = environment.getexternalstoragedirectory().getabsolutepath();     mfilename += "/audiorecordtest.mp4";     mrecorder = new mediarecorder();     mrecorder.setaudiosource(mediarecorder.audiosource.mic);     mrecorder.setoutputformat(mediarecorder.outputformat.mpeg_4);     mrecorder.setoutputfile(mfilename);      mrecorder.setaudioencoder(mediarecorder.audioencoder.amr_nb);      try {         mrecorder.prepare();     } catch (ioexception e) {         log.e(log_tag, "prepare() failed");     }      mrecorder.start(); }  private void stoprecording() {     mrecorder.stop();     mrecorder.release();     mrecorder = null; }