eSpeak - Speech Synthesizer - http://espeak.sourceforge.net/

espeak_voices.txt

Pty Language Age/Gender VoiceName          File          Other Languages
 2  en-gb          M  english              en            (en-uk 2)(en 2)
 3  en-uk          M  english-mb-en1       mb/mb-en1     (en 2)
 2  en-us          M  english-us           en-us         (en-r 5)(en 3)
 5  en-sc          M  en-scottish          other/en-sc   (en 4)
 5  en             M  default              default       
 5  en-uk-north    M  english-north        other/en-n    (en-uk 3)(en 5)
 5  en-uk-rp       M  english_rp           other/en-rp   (en-uk 4)(en 5)
 5  en-us          M  us-mbrola-2          mb/mb-us2     (en 7)
 5  en-us          F  us-mbrola-1          mb/mb-us1     (en 8)
 5  en-us          M  us-mbrola-3          mb/mb-us3     (en 8)
 9  en             M  en-german            mb/mb-de4-en  
 9  en             F  en-german-5          mb/mb-de5-en  
 9  en             M  en-greek             mb/mb-gr2-en  
 9  en             M  en-romanian          mb/mb-ro1-en  
 5  en-uk-wmids    M  english_wmids        other/en-wm   (en-uk 9)(en 9)
10  en             M  en-dutch             mb/mb-nl2-en  
10  en             F  en-french            mb/mb-fr4-en  
10  en             M  en-french            mb/mb-fr1-en  
10  en             F  en-hungarian         mb/mb-hu1-en  
10  en             F  en-swedish-f         mb/mb-sw2-en  
 5  en-wi          M  en-westindies        other/en-wi   (en-uk 4)(en 10)
11  en             M  en-afrikaans         mb/mb-af1-en  
11  en             F  en-polish            mb/mb-pl1-en  
11  en             M  en-swedish           mb/mb-sw1-en  

$ brew install espeak
$ espeak --voices=en`

Speak at 2msec/words, capital letters pitch increase of 20, output IPA phonemes to file phonems.txt, input from text.txt, using voice en-us, pipe speech synthesis to ffmpeg output to convert to mp3 format out.mp3. No stdout, execute quietly.

$ espeak -f text.txt -v en-us -g2 -k20 --ipa --phonout=phonems.txt --stdout | ffmpeg -loglevel panic -y -i - -ar 44100 -ac 2 -ab 128k -f mp3 out.mp3