A multiclip is a set of clips grouped together and synchronized by a common sync frame. Each clip in a multiclip is known as an angle, and you can switch between angles as necessary. The angle whose video and audio is seen and heard when you play your sequence is called the active angle.

Multiclips can be used to edit footage from multicamera shoots or other synchronized footage in real time. For example, if you shot a live concert with four different cameras, you can synchronize the angles together into a single multiclip and cut between them in real time.
You can also group unrelated footage together for real-time montage editing (such as for music videos). For example, if you are editing a music video, you could add several angles of abstract visuals and cut to those angles on specific beats of the music.
Working with multiclips in Final Cut Pro is a flexible and fluid process. While the active angle plays in the Canvas, you can also view all angles playing simultaneously in the Viewer. You can add or remove angles from a multiclip at any time, and easily adjust the synchronization between angles after you have created the multiclip.

Multiclips have the following limitations and requirements:
Clips in a multiclip are not required to have the same duration, but they must all use the same codec, image dimensions, and frame rate.
Important: The same capture preset should be used for all footage you plan to make into a multiclip.
Multiclips can be created from any clips in the Browser: video and audio clips, still images and graphics, and even other multiclips.
Multiclips can have a maximum of 128 angles, but only the first 16 can be played back in real time.
Each angle can be a clip with video and audio, video only, or audio only.
A multiclip can have only one active video item and up to 24 active audio items at a time.
The number of audio items in a multiclip is determined by the angle with the highest number of audio items.
For example, consider a multiclip that contains three angles with the following number of items:
The resulting multiclip has 8 audio items. Extra empty audio items are added to angles 1 and 2 so that all angles have the same number of audio items.
The active video and audio items can be independently switched to different angles.