How to write Output of AUGraph to an External AudioFile of WAV or AIF formats?

In my iOS app i am playing a MIDI file using Music Player & Music Sequence. And i'm getting AUGraph here by calling "MusicSequenceGetAUGraph" method of the Music Sequence. Now i want to save the same Output of this AUGraph to an External File. How can i do that? Can any one help me?

Here i'm not using any Nodes to create AUGraph. I'm getting the Graph directly from Music Sequence.

Thanks in Advance.

Here is my AUGraph

AudioUnitGraph 0x246104F:

Member Nodes:

node 1: 'aumu' 'samp' 'appl', instance 0x1c558830 O I
node 2: 'auou' 'rioc' 'appl', instance 0x1c54a550 O I

Connections:

node   1 bus   0 => node   2 bus   0  [ 2 ch,  44100 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved]

CurrentState: mLastUpdateError=0, eventsToProcess=F, isRunning=T (1)

There is an example here of writing the output of an AUGraph to a file