Now I am using Apogee Metarecorder.
I had bad surprises, but that in fact has nothing to do with app itself.
If (during recording) you push and hold home button - be sure - recording will be interrupted and stopped. Therefore suggestion - disable SIRI when recording
My pretaping routine:
1. Home - Settings - Do not disturb
2. Hardware silence switch on the phone - set to silent
3. Home - Settings - General - Accessibility - Home button - Siri - OFF
4. best one to end up: Home - Settings - Airplane mode - Enable it
Good luck.
in fact I have separate iPhone for recording
BTW if you tape with Apogee - tape it to CAF format. This format allows to record files bigger than 2GB. Wav files are limited up to 2GB and recording stops.