[Tammy Briody] “I have looked at several tutorials/books and it appears multicam only allows you to use one audio source that is why I made a compound audio source clip. I need to use all my soruces because I record the String quartet on on source, officiant on another, readers on another and groom on another. I need to mix all these audio sources together.”
One suggestion would be to make a polyphonic file, which is to say, one file that has all of your channels of the recording, and sync that in a multi clip angle.
If not you can certainly listen to whatever channels you want from separate or combined audio only angles, in the multilcip, and not just one at a time.
Here’s a multiclip I made just yesterday to get some window burns made. The video has 8 channels of audio, and there’s two files of four channel audio (16 channels of available audio). For now, I just need a few channels for transcription.
Here’s how I have it setup in the inspector:

Here’s what the multiclip looks like which only has one angle for now. Later, I will add and sync a second camera angle:

In the timeline, I can mix whatever channels I’d like by expanding the audio components like this:

I can the turn on more channels, and use those in the mix too:
Here’s the inspector:

Here’s the corresponding timeline:

Multiclips in FCPX are wicked powerful.
Jeremy