objective-c - Recording problem in headphone mode

Question

Purpose: It needs to be achieved, playing background music (can be paused, the volume can be adjusted), and recording sound at the same time
Problem: In plug-in headset mode, background music cannot be recorded, only sound can be recorded.
Me Solutions that come to mind: It is really impossible to record background music. We can only use synthesis. Record the sound first, and then synthesize the background music and sound together. But for current needs, you can pause and adjust the background sound size. The steps for synthesis are too cumbersome.

Help: Do you have any good suggestions?