Same problem here! The audio quality of recordings donr with FP4 is very disappointing 
I’m a musician and I like to use my phone to record spontaneous ideas and snippets of sessions, as well as videos for my social media accounts and students, but the sound quality is very disappointing to unusable.
Honestly, the audio recording app that came with the phone is completely unusable, because the quality is so extremely low.
I’ve tried simplemobiletool’s audio recording app, which is a bit better, but still rubbish when it comes to loud environments i.e. a session. Also volume is really low.
I’ve tried the OpenCamera app for video recording and while the unprocessed audio quality is much better, it is extremely low in volume.
I would really appreciate some help here or a patch, since good quality audio recordings should be standard for modern smartphones. I really hope the team is working on a solution!
I feel like the microphones are technically good, it’s just that the software can’t access them or processes the recordings to death.