Twilio: programmatically join conference and play <Say> command or <Play> sound file?

I have two users and I joined them both into a <Conference>.

I would like to have a robot join the <Conference> and then make an announcement.

There are two approaches I'm considering:

1. Take everyone in the conference, redirect them to a TwiML that plays a sound, and then move them back into the Conference.

2. Create a bot that somehow joins the Conference and plays TwiML, but it's not clear for me, from the documentation, how to do that.