Seriously, it never occurred to me that you could choose an appealing voice for your inner monologue, mine has always been a neutral version of my real voice. Stranger since I subvocalize while reading, and as a kid, the voice would actually act and change for each character.

Now I wonder if your reading speed can improve by choosing a voice from here https://tvtropes.org/pmwiki/pmwiki.php/Main/MotorMouth