Setting conference_set_auto_outcall_flags=mute only sets the initial state to muted. The attendees can still press 0 to unmute (if the key mappings are left at their default values). So you can use send_dtmf to unmute the loopback extension, and then stream the audio. E.g., expanding my code from earlier: streamwelcomefile.lua <code> if ( session:ready() ) then session:answer(); -- Must wait a couple seconds after connecting before sending DTMF, -- or it will get lost: session:sleep(2000) -- Unmute this attendee: session:execute("send_dtmf","0@200") session:sleep(1000) session:streamFile("ivr/8000/ivr-welcome.wav"); session:streamFile("ivr/8000/ivr-thank_you_for_calling.wav"); session:hangup("NORMAL_CLEARING"); end </code>