Duplicating Sound Channels

Anyone know if it's possible to easily copy and paste one sound channel into another for multiple clips at once in iMovie? I shot a small documentary, parts of which we only used one mike/channel for... Wondering If you have to do each clip at a time..any suggestions would be most appreciated!

A stereo synthesizer would be better. There's free plug-ins to do that included with Amadeus Pro ($40), and you could probably find one to work with Audacity (free) with a little hunting.