AVID - How to change the aspect ratio on the entire edited timeline

In AVID if your clip is the wrong size and you need to change the source settings do the following

First Duplicate your timeline

Go to >Edit>Duplicate

Go to Bin>Set Bin Display

Choose to Show Reference Clips

Click OK

The clip or clips that are referenced in the timeline will appear in the bin. Right click on one of them you want to change the aspect ratio of and choose >Source Settings

Set to Pilarbox/Letterbox or whatever

Click Apply

Right click on the sequence and choose

Refresh Sequence > All

The sequence will change to the new aspect ratio