It is not more possible to record in the background since Android 9. I use for reading the audio data the Read function in the class Android.Media.AudioRecord. After one minute in the background the API read zeros as audio data. All versions lower Android 9 worked fine. I found this reference concerning audio permissions from Android: https://android-review.googlesource.com/c/platform/system/sepolicy/+/577303
Some recorder apps can still record in the background. My guese is they compile the apps with a lower target sdk. Have somebody more informations what is in the future possible and what not. Are there an other way to record in the background?