My sister and I ( who live 1500 miles apart)are trying to play piano/cello sonatas using FaceTime on our iPads with not much success. I'm the piano player and can hear her cello just fine. The piano does not come through loud enough on her iPad for us to stay together. She has used the speaker on the iPad, earphones, amplified the sound with add-on amplifiers. Do I need to use an external mic?And if so, which one?