Any screencasting apps thatll let me get audio only? who has a method for me to record the audio which is playing to an mp3 or whatever? i just wanna bounce these sounds im listening to to another program but im not sure how to demux videos and its hard to use keywords to find a screen casting app that does what im looking for.  thanks! hey also... if anyone has details on some android audio interface techniques to record line out 3.5mm to like some kind of usb otg connected interface, i would really appreciate this.
https://play.google.com/store/apps/details?id=com.nll.asr

ASR works good for me. Hope you get what you needed. It can record audio from apps running in background.