Awesome post and awesome assistance, you guys!! Thanks!!!! It solved precisely a problem that I was about to try to tackle. Here's how I used it:
I've found that you can run (at least) four audio tracks at a time. You can have one in music, one in special effects, one in narration, and one in the internal track of a slide. This means that you can collect bits and pieces of sound that you want to play at the same time (for example, a conversation taking place at a train station) without having to have any of the people in the same place, much less at the train station, when you record their bits. Just run around with a recorder (or in my case, a mobile phone) to the train station, and then visit all your friends, tell them the bit you want them to say (in my case, Happy Birthday Hannah!!!!), and then go home and load all the bits and pieces into the different tracks. And voilá!!! A crowd of the birthday girl's friends all screaming Happy Birthday to her, together, as if they were all standing in a big group on the steps of the train station.
Great stuff, Merv!