...From v3.16 onwards the RISC OS version of eSpeak is not included in the Pluto download, but separately in the Files espeak directory. The espeak project itself is on https://espeak.sourceforge.net/ but seems currently dormant.
For full details of all updates since v3.06b, please see the Pluto Web Site on http://www.avisoft.f9.co.uk/pluto/