Alter the accent menu to add more special characters

Software
1

Hi, Can someone please tell me where the accent menu lives and how I can add more characters to it? I would like to add some IPA (International Phonetic Alphabet) characters so that they show up when I hold down a key. Like when you hold down ‘a’ to get àáâä, etc.

Thanks!

2

The Text Replacements section in the Keyboard System Preferences pane may be useful here.

I also found this on the Google: Using IPA fonts with Mac OS X: The Comprehensive Guide