One way to do it is to add a target_play_music entity like this
Code:
{
"classname" "target_play_music"
"targetname" "WhateverNameYouFancy"
"music" "music/mymusic.mp3"
"origin" "x y z"
}
and then do a
Code:
use ( "WhateverNameYouFancy" );
from within the script. Don't know if there's a better way than that (probably so).