kAMM_PlayAndRecord is a CocosDenshion constant so you won’t find much info searching on that. It maps to kAudioSessionCategory_PlayAndRecord. This Apple documentation explains why your audio is quiet and how to fix the problem:
The Redirecting Output Audio section, specifically
When using the “play and record” category—which indicates your intention to use both audio input and output—output audio normally goes to the receiver. You can redirect this audio to the speaker at the bottom of the phone in two ways:
Then they give code to redirect output to the main speaker.
doesn’t appear to need un-setting after I switch back to kAMM_FxPlusMusicIfNoOtherAudio mode (document says it is reset when the audio mode is next changed so that makes sense).
I’ve made the above change just run on the iPhone, but it didn’t seem to have any effect on iPad (which doesn’t have the phone receiver speaker to route the audio too, so doesn’t suffer the change anyway).