Todd,
What you want to achieve is entirely possible with Xara and a small amount of additional code. A while back now Acorn and I helped develop an Audio Player Plugin:
https://initiostar.co.uk/demo/Jukebox/
The current structure of your site has an 'interviews' page with what looks like individual pages for each of the 300 + interviews, where each individual page also opens a popup to the audio track (i.e. interview).
The Audio Player we developed could be extended to allow you to map, on 1-2-1 basis, each of your interviews. Not the finished demo, but here is an example:
https://initiostar.co.uk/demo/AudioPage/
The style is simply one whereby you have an interview page that lists all the interviews; this could easily be your ABC list as is. Each link opens a page-within-the-page to save the visitor jumping back and forth. Each interview page has the audio track and any other information of your choice, but importantly, you are using a template for each interview page which makes any transition a bit easier.
Where you have a long list, some additional code needs to be added so that the interviewee page window scrolls to the top of the interview page.
A couple of other sites that have used the audio player concept are:
https://www.waterwaysongs.info/ and
http://www.jonphilibert.com/jukebox.htm
Give the ideas some further thought and come back if you want a copy of the demo.
Gary