Set waiting tone for asterisk agi function processing

If you use phpagi, you have do something like this

$agi->set_music(true,"myholdclass")
...
$agi->set_music(false)

http://phpagi.sourceforge.net/phpagi2/docs/phpAGI/AGI.html#methodset_music

Sure you need first describe myholdclass in /etc/asterisk/musiconhold.conf