say

osascript -e 'set volume 7'   # 0-10
    -e    # one line script without looking for a filename

say hello
say -v 'fred' My name is Fred.
    -v 'siri'
    -v 'Good News'
    -v 'bad news'
    -i    # highlight words as they are spoken.
    -f    # read a speciific file.
    -r rate, --rate=rate    # in words per minute.
    -o out.aiff, --output-file=file    # specify path for audio file to be written.
    -a name, --audio-device=name    # pick a specific audio device to play.  ? to get list.
    --progress    # get a progress bar during synthesis.