title: Bad quality after multiple fade effect with pydub
body: <p>I would like to generate workout mp3 file with music in the background and instructions at some timing (ex. "push harder", "do another repetition !")</p>
  
  <p>I generate the instruction with pico2wave and assemble them with pydub.</p>
  
  <p>I do this :</p>
  
  <pre><code>for timing,phrase in phrases.items():
          fileToAdd = pydub.AudioSegment.from_file(rep+"/"+str(timing)+".wav")
          finalFile = finalFile.fade(to_gain=-35, start=(timing*1000)-500, duration=500) # on diminue la chanson, une demi seconde avant
          finalFile = finalFile.fade(to_gain=+35, start=(timing*1000)+len(fileToAdd), duration=500) 
          fichierFinal = fichierFinal.overlay(fileToAdd,position=timing*1000) 
  </code></pre>
  
  <p>The result file has a VERY bad quality. I try to remove the "fade effect" and the quality is good (but I don't hear very well the "instructions")</p>
  
  <p>How can I change this ? Can I easily make a fade out and fade in effect ?</p>
  
  <p>Thank you,</p>
  
  <p>Regards,</p>
  
  <p>Axel</p>