How do I increase audio sound on my app for recording phone calls? I have an Echo phone and downloaded an app for recording phone calls, both received and made myself. When it records, my voice is very loud, but you can barely hear the other line unless it is on speaker phone. Is there a way of increasing there level without using speaker? I record phone interviews I do and it is much easier just using the headset and not using the speakerphone...cuts out parts of our conversation.
The recording works by using the microphone.  You're talking straight into the mic and thus are much louder than the sound that reaches the mic from the ear speaker.

You'll need to use an app that actually records the incoming call and not simply what it picks up from the mic.  Check out this question, I believe it includes a couple such apps in the answers.