Cant hear song playback while recording with external USB Interface Mic in Garageband

Question

Hi there
There must be something wrong with my settings in Gargaeband/Mac Sound Settings.
I have Garageband 9 (V5.1) running a song I have already recorded using a USB keyboard.
I want to record using my external mic and my USB Audio Interface, so
I select New Track> Real Instrument
I plug in my Yamaha Audiogram 3 USB AUdio Interface and I get a pop up stating
"Garageband is scanning your system for audio devices, and has detected a device named "USB Audio Codec"
If you want to use this device do not disconnect it during the scanning process.
Do you want to use this devise No/Yes."
I select Yes and INPUT SOURCE changes from
Mono 1 (Built-in Microphone)
to
Mono 1 (USB Audio CODEC)
I can see the signal lights lighting up on the audiogram 3 when I talk into the mic, so theres no problem there.
Also when I hit record I can record audio using the mic, and can see the levels (and the audio wave I am creating being drawn on the screen) but I cannot hear the track itself when I am recording using the mic. Nor can I hear the track or the new mic recorded audio AFTER I have hit stop.
The only way to hear the song again with the newly recorded mic track is to unplug the Audiogram 3 (Then I get another Pop-up stating
"The audio device "USB Audio CODEC" has been disconnected!
Do you want to switch to Built-in Audio or quit Garageband?"
I select USE BUILT-IN AUDIO)
Then the input source changes back to
Mono 1 (Built-in Microphone)
And I can hear the track again.
So my problem as you can see if that I cant hear the track while recording using the microphone with the Audiogram 3.
But I can record video with audio using the audiogram 3 USB Audio Inteface and mic using photobooth when I select change Sound>Input to USB Audio Codec in system preferences
It therefore assume it must be a problem with the internal audio settings of the mac/garageband.
Can anyone advise?
thanks!

Answer 1

I can see the signal lights lighting up on the audiogram 3 when I talk into the mic, so theres no problem there.
Also when I hit record I can record audio using the mic, and can see the levels (and the audio wave I am creating being drawn on the screen) but I cannot hear the track itself when I am recording using the mic. Nor can I hear the track or the new mic recorded audio AFTER I have hit stop.
In order to hear yourself while you are recording, you need to set Monitor to "ON" under the Track Info panel.
Also, what are your sound output settings?  It sounds like you haven't selected the right output source. 
If your speakers or headphones are plugged into your audio interface, then you need to go into Preferences -> Audio/MIDI and select your audio interface under Output as well as Input.  If your speakers or headphones are built-in or plugged directly into your computer, then you need to select Built-In under Output. 
I have a sneaky feeling that you are in the latter scenario, and that when you plug in your audio interface Garageband is automatically switching both Input and Output over to your interface, which means no sound output as long as the interface is plugged in.