By default Icecast 2 will not provide a status-json.xsl file, and that's a bit problematic if you're looking to perform a GET request on your Icecast 2 server.
You need to update the /etc/icecast2/icecast.xml file
<http-headers>
<header name="Access-Control-Allow-Origin" value="*" />
<header name="Access-Control-Allow-Headers" value="*" />
<header name="Access-Control-Allow-Methods" value="POST, GET, OPTIONS" />
</http-headers>
Do not forget to restart your icecast server after editing this configuration file.
You can now query the endpoint /status-json.xsl to get a JSON response including your current playing song.