espeak-ruby

gem "espeak-ruby", require: "espeak"

# Speaks "YO!"
speech = ESpeak::Speech.new("YO!")
speech.speak # invokes espeak

# Creates hello-de.mp3 file
speech = ESpeak::Speech.new("Hallo Welt", voice: "de")
speech.save("hello-de.mp3") # invokes espeak + lame

# Lists voices
ESpeak::Voice.all.map { |v| v.language } # ["af", "bs", "ca", "cs", "cy", "da", "de", "el", "en", "en-sc", "en-uk", "en-uk-north", "en-uk-rp", "en-uk-wmids", "en-us", "en-wi", "eo", "es", "es-la", "fi", "fr", "fr-be", "grc", "hi", "hr", "hu", "hy", "hy", "id", "is", "it", "jbo", "ka", "kn", "ku", "la", "lv", "mk", "ml", "nci", "nl", "no", "pap", "pl", "pt", "pt-pt", "ro", "ru", "sk", "sq", "sr", "sv", "sw", "ta", "tr", "vi", "zh", "zh-yue"]

# Find particular voice
ESpeak::Voice.find_by_language('en') #<ESpeak::Voice:0x007fe1d3806be8 @language="en", @name="default", @gender="M", @file="default">

:voice     => 'en'    # use voice file of this name from espeak-data/voices
:pitch     => 50      # pitch adjustment, 0 to 99
:speed     => 170     # speed in words per minute, 80 to 370
:capital   => 170     # increase emphasis (pitch) of capitalized words, 1 to 40 (for natural sound, can go higher)
:amplitude => 150     # amplitude (volume) adjustment, 0 to 200

Speech.new("Zdravo svete", voice: "sr", pitch: 90, speed: 200).speak