(Cross-posted from the TV Guidance blog)
I've talked a few times about the differences between real laughter and canned laughter in television (which are often spoken of as though they're the same thing) without really illustrating what I mean. So I thought I'd put together a video to give an idea of how a multi-camera TV soundtrack is enhanced in post-production. I had a copy of an old WKRP episode in two different soundtracks: the "unsweetened" version, with no sounds added that were not recorded live on the set, and the "sweetened" version for final broadcast, with extra laughter and music added. I already showed a scene from this episode with and without music. What I've done here is put some excerpts side by side, along with some captions pointing out what's been added and whether the laughter is real or canned.
Now, the sound of a laugh track was different and more obvious 30 years ago, and there were differences in terms of sound mixing. (Today, it's more likely for ambient sounds, like crowd background noise, to be added. Back then there was basically nothing except the dialogue and laughter.) But the basic differences seem to be the same. First, in the final mix, the sound of the real audience laughter is sometimes a bit different, perhaps because of added echo. And sometimes the mixer adds in a canned laugh track, though this is not one of those episodes where the audience didn't laugh much. But you'll notice that the reason for the added laughter isn't always the same from clip to clip. Reasons for adding canned laughter include:
1) The audience didn't laugh at a joke and the producers want to keep it in. (Sometimes because it wasn't funny, as Woody Allen protests to Tony Roberts in Annie Hall, but sometimes because the joke was too much of a throwaway for the audience to laugh at it.) The extra laughter allows the joke to stay in without giving the impression that it fell flat compared to the jokes that did get big laughs.
2) The scene, or part of a scene, was done as a pickup after the audience went home, and the laugh track is inserted to make it fit, sonically, with the rest of the episode.
3) In a couple of spots in this video, very mild, almost inaudible laughs are inserted to cover a long pause and keep the sound from being "dead." It's very similar to the way one-camera shows use ambient noise or -- especially -- music.
4) Sometimes a laugh is extended a bit so it will last into the next shot. This is done to create a smoother transition between two shots that might come from different takes.
5) Finally, in the last clip from this video, the audience applauds after a joke. The producers apparently didn't want the applause, so they replaced the applause with a laugh track. So in this case the laugh track is used to tone down the audience response, which is something that is still done today.