How to record audio without using microphone in android?

Question

Java

I have a music app. It contains recorded sounds that can be played back simultaneously. I need to record them without the help of a microphone, so that there is no extraneous noise. I know there are apps like "Music Maker JAM" in google play store, but I don't understand how they made this possible. Any ideas?

Answer 1

https://soundcloud.com/leonid-bogolubov/android-de...
developer.alexanderklimov.ru/android/theory/soundp...