Misunderstanding MOH: also playing internal

I built my own dialplan on an asterisk 1.8 machine. I have:

  • two DAHDI-Channels connecting to the world
  • two DAHDI-Channels to a fax machine and an analog handset
  • some SIP-Phones.

I want MOH to play to the world only, on attended transfer the external callee should here the MOH and the internal lines should her a ringing sound.

As I think I totally mixed things up - can anyone give me a hint where I have to do what?

Some more details:

I need to set MOH with
because I have to switch the musicclass during the lifetime of the call.

The Dial commands in my dialplan are:

and I think the m here is the problem. No idea how to fix that - I tried almost anything.

Thanks in advance, best regards,