If you're on Mac, you can use `say`, e.g.,

    say "This is a test message" --voice="Bubbles"

EDIT: I'm having way too much fun with this lol

    say "This is a test message" --voice="Organ"
    say "This is a test message" --voice="Good News"
    say "This is a test message" --voice="Bad News"
    say "This is a test message" --voice="Jester"