Now we'll make the sound file using the free sound editor program Audacity.
Audacity is a very cool tool and it's completely FREE!!! Its commercially available cousin is Sony Sound Forge which will run you $250, and used to cost a lot more than that. Here's more on Audacity from Wikipedia.
Anyway, here's the steps:
1. First you want to fire up Audacity and record the Easy button into your PC using a microphone, or into the mic of a notebook computer. Just click the "record" button on Audacity and a window will open and start recording.
2. Record the electronic whoopee cushion into Audacity. Just click "record" and a new audio track will open.
3. Open a blank audio track (Project>New Audio Track.) This will be our working file and eventually our final sound clip.
4. Pick out some or all of the whoopee sounds and paste them into the final sound clip window. You can cut and paste the sounds to your hearts content. You can use the special effects to add echo, and other things. Just fool around with it and keep playing it back. You can easily undo any effects you add, and you can also preview effects to see how they sound. You can adjust the volume of selected parts of the sound file, too. I used the pitch shifting effect to get something cool. If you understand music and pitch, you can literally duplicate any song.
5. When that's done, select (highlight) the Easy button sound, copy it, and then paste it at the end of the modified whoopee cushion sound in the final sound clip. Play it back and make a final edit to adjust the spacing between the sounds (add silence,) and then you'll want to save the sound file for posterity as an mp3 file (File>Export As MP3,) although you can save it in other formats as well. You can hear the audio file I made in the final step of this instructable.
6. Play back the completed soundtrack while recording it into the sound module.