Hope this is not OT. A few podcast hosts offer dynamic ad insertion. Your mp3 file stays untouched, the ad gets inserted automatically via their servers. As an alternative you can embed the ad clip in your mp3: that means cutting the ad clip out once the campaign is over and re-create the original mp3 file. What is the best way to go for this second option? What tools would you recommend to speed up the workflow? What caveats? Thanks.