This is a module I built early this year.
It is an Arduino driving a SpeakJet chip to produce allophones and weird synth sounds.

It works on an algorithm coded in Arduino, which is basically a sequence with a variable, the slide potentiometer position amount, which makes the sound change.

The rythm and velocity must be changed into the code.
It has an LCD to display the amount of the slide potentiometer. It says "Voice Pitch" but it could be anything.
The first slide potentiometer is the volume.

Based on the sequence you can produce robot voices.
The easy way should be to add another chip which translates text into sound.