Raspberry pi can speak using eSpeak library, so what is the big deal you ask? For those who are not familiar with eSpeak library, it is an open source speech synthesizer that is available for a lot of platforms. Simulink provides a visual programming language which uses the eSpeak library under the hood so that non-programming folks like me can still use the library effectively.
Here is a 90 second Facebook video that shows how to use the eSpeak block in Simulink and make your Raspberry Pi speak (in a voice that reminded me of my favorite Astrophysicist) https://www.facebook.com/MATLAB/videos/10152971056041641
Here are the files that I used to adopt the eSpeak library and its commands via Simulink and make my Raspberry Pi speak in a female voice. For more cool projects shared by community members visit MATLAB Simulink.