WaitMusicOnHold() — Waits the specified number of seconds, playing music on hold
Plays hold music for the specified number of seconds. If no hold music is available, the delay will still occur but with no sound.
Returns 0 when done, or
-1 on hangup.
; allow caller to hear Music on Hold for five minutes
exten => 123,1,Answer()
exten => 123,2,WaitMusicOnHold(300)
exten => 123,3,Hangup()