error message that says "Unhandled Exception"

This is an error bubbling up from macOS. There are cyclic links in your file system, probably involving a symbolic link pointing back to itself. Synfire merely happens to stumble upon it during startup.

If you list all symbolic links on your Mac, you might find the culprit and remove it. Something like

find . -type l -ls

Any other software that would come across the corrupted symlink on your hard drive would throw this message, too. It is not specific to Synfire.

The solution is to find and remove that link.

If you google for "Too many levels of symbolic links", you'll find several suggestions as to how that could be done, for example:

(http://www.ieor.iitb.ac.in/files/faculty/amahajan/howtos/too_many_level…)

Try this one in your home directory:

find -L  .  -type l

Replace 'Config' with anything you expect in the filename, e.g. 'Tonality.catalog'.

Since I don't have corrupt symlinks on my drive, I can't test.

EDIT: Had to correct the command (see above) last character is a small L

What happens when you navigate with Finder to the file? (/Users/mikeb/Documents/Synfire Pro/Config/Tonality.catalog)

Or if you type

ls -l /Users/mikeb/Documents/Synfire Pro/Config/Tonality.catalog

That might show a more helpful error message in Terminal

A solution to this has been found:

(https://users.cognitone.com/kb/message-too-many-levels-symbolic-links-m…)

Hope it helps.