Apple Final Cut Pro 7 - Manual (Page 981)

Installing Third-Party Audio Units Filters
If you install third-party Audio Units filters, they will be available to all applications on
your computer that are capable of using them, including Final Cut Pro. You only need to
install them in one location.
Before purchasing third-party Audio Units filters for use with Final Cut Pro, check with
the third-party manufacturer to make sure the filters are compatible. Currently,
Final Cut Pro works only with Audio Units filters that are capable of accepting mono audio
as input and can output a mono signal. Also, Audio Units filters that don’t support certain
properties required by Final Cut Pro for real-time playback may require rendering before
playback.
For information on how to install third-party audio filters, see the information that came
with the filters.
Important: If you open a project that uses a filter that is not installed on your computer,
Final Cut Pro warns you that the filter is missing. If you install the filter and open
Final Cut Pro, the warning goes away. Clips that have missing filters applied still play back
in the Timeline, but the effects are missing.
981 Chapter 59 Using Audio Filters