So I just bought a lightling to USB adapter so I can connect my digital piano (Yamaha P-125) to my iPad. My main use of this is to be able to use software like SimplyPiano. The app teaches you how to play the piano by asking you to play a note and waiting to hear the sound via the microphone. That's not very accurate (especially when playing chords). In order to be more precise they recommend to connect your keyboard to the iPad so they communicate via the MIDI interface. My problem is actually with GarageBand. I can hear both the normal piano sound and the instrument that i've chosen in the app, at the same time. How do I only hear the instrument in the app?

Thank you so much! Now I feel a bit ashamed because I haven't read the manuals. 🙈