Inbound Calls and AMI (unbridge)

I’m not very experienced with asterisk but I’ve built a dialplan which deals with incoming calls. The calls come (are routed) from an inbound trunk. At some point during the dialplan execution I dial a terminating number.

After a set time, say 20 minutes, I would like to unbridge the connection to the terminating number, but NOT HANGUP. The communication between the caller and the callee should stop. The outbound channel (callee) should hear some background music while the inbound channel, the one that was routed to my system should go through some specific dialplan, after which connect the two channels so they can communicate again.

I was told this was possible and I should use: AMI Action Redirect with ExtraChannel feature. How would I integrate AMI into this automatic scenario?