MD was able to speak again after I installed ESpeak, but is used a very deep robotic voice. It seemed to ignore the settings that I set on the voice.
So, I installed Vocaliser (from the play store, buying the voice 'Kate'). Initially MD did not seem to recognise the new default speech engine and carried on with its deep robotic voice. I uninstalled espeak. That didn't help. I rebooted the phone and then MD started to use the mellifluous voice of Kate from Vocaliser.