Garageband picking up playback audio from piano

Hi! I have a question around recording on Garageband.

I have a Yamaha p-125 digital piano which I plug directly into my ipad for Garageband. This is done through a USB cable and lightning adapter.

I compose music and really like the piano & string voices that are already on the piano. I prefer them to Garageband's own instruments.

I've tried recording with the audio recording option which has worked really nicely for just one track/layer.

When I went to record a second layer (this time choosing strings on my piano), it recorded the new song but also the piano playback in the background. I've tried changing the settings, using different headphones etc. but nothing seems to work. I wear headphones which are plugged into my piano. I can't seem to hear anything if I plug them into my ipad when the piano is connected.

Basically I want to be able to record separate layers without the new layer recording the playback from the first layer. This is so I can adjust the volume/velocity of the strings against the first piano layer =]

Is there a way of telling Garageband to just record the piano input and not the playback at the same time?

This definitely doesn't have anything to do with background noise as I believe it's only recording through the cable connector and not the ipads mic.

Thanks so much in advance for your help!

Amy :)