In the classic movie musical Singing in the Rain, Jean Hagen plays Lina Lamont, a glamorous silent film star who, at the advent of talking pictures, is at risk of losing her career because she has a voice as ugly as her face is beautiful. The lesson is that even fantastic video footage can come to naught if the audio can't keep pace.
In the early chapters of this book, we repeatedly stress the importance of capturing quality audio. This might mean recording audio from multiple sources or employing external microphones to capture the audio up close and personal, even when the camera isn't.
Regardless, however, of how much care you take to obtain the best audio possible, sometimes "stuff happens." This chapter covers what iMovie offers to help you work around some of that stuff, including adjusting volume, normalizing volume across a clip (or clips), and setting beat markers to synchronize clips (and stills) with points in an audio track.
iMovie doesn't provide some audio editing features that were available in the iMovieHD and earlier versions, but it does include some new capabilities that are more useful, in general. For example, you can't manually ramp (gradually alter) a clip's audio up and down through a clip, but you can normalize volume across the clips ...