osascript -e 'say "[[rate 160]] apples and pairs" using "Zarvox"'
It seems to be like 160 is the default speed, you can go quite a lot slower but I've found that above about 300 things start getting unintelligible. You can also use [[emph +]] and [[emph -]] directly before a word to augment or subtract emphasis from it.
The [shell] object helps you run command lines as if you were typing into Apple's Terminal application. I really only use it to run applescripts but I'm sure it is capable of a lot more.
I have a new question about the [shell] object if you don't mind.
If I use plain old AppleScript in my Terminal I can run multiple texts simultaneously. With the shell object I can't. I have two objects set up and send each a different text at the same time. The texts are spoken one after the other.
Is this a Max limitation, a shell limitation... or is there a workaround??