It should be possible to run the results of Unix speak.c through a real (or emulated) Votrax Type 'n Talk unit. I know MAME has emulation of said unit, and while it isn't perfect, its pretty understandable.

I took a shot at making a modernized port of speak.c myself not long after the code was found, but it didn't get very far, sadly. I couldn't figure out an easy way of dealing with the multiple-character character constants.