I have installed software for converting text to speech in Ubuntu-gnome 15.04 linux. I did this to install voice menus for the rockbox firmare/software on my sansa clip+ audio player.
Installing the software
sudo apt-get install gespeaker
sudo apt-get install mbrola
Install mbrola english-us voices
sudo apt-get install mbrola-us*
voices are installed at /usr/share/mbrola
espeak data folder: /usr/lib/x86_64-linux-gnu/espeak-data
sudo ln -s /usr/lib/
see data folder reference https://bugs.launchpad.net/ubuntu/+source/gespeaker/+bug/919577
espeak -v mb-en1 “Hello world, process, I am an Aggie”
mbrola: FATAL ERROR : cannot find file /usr/share/mbrola/voices/en1
sudo ln -s /usr/share/mbrola /usr/share/mbrola/voices
espeak -s 140 -v mb-us2 “process, I believe in God the Father almighty, maker of heaven and earth.'”
or
espeak -s 140 -v us-mbrola-2 “process, I believe in God the Father almighty, maker of heaven and earth.'”
espeak -s 140 -v english-us ‘process, I believe in God the Father almighty, maker of heaven and earth.’
List installed english voices
espeak –voices=en
Documentation Location
/usr/share/doc
Additional information for improving espeak sound
http://www.freelists.org/post/nvda/Improving-the-sound-of-eSpeak