demo.js

var twilio = require('twilio');

var client = twilio('your account sid', 'your auth token');

// Call everyone that texted a number you just bought - remember, for this to work,
// this needs to be a number you just bought, that only this room full of people have
// texted
client.listMessages({
    to:'your twilio number'
}, function(err, data) {
    data.messages.forEach(function(message) {
        client.makeCall({
            to:message.from,
            from:'your twilio number',
            url:'http://someserver.com/twiml.php' // TwiML instructions for the outbound call
        });
    });
});

twiml.php

<?php header('Content-Type:text/xml'); ?>
<!-- Would be easy to just generate this XML from a node server - doesn't need to be PHP -->
<Response>
    <Play>http://someserver.com/audio/zelda.mp3</Play>
</Response>