I have found these Neumann tools invaluable in recent months, and can heartily recommend them as a very worthwhile addition to a phone or tablet. The app design is elegant and intuitive, the functions are accurate and real-world-useful and, best of all, the Neumann Recording Tools app is entirely free. What’s not to like?
Well there's this. On my Nexus 5x running Android 8.1 when you start the app the usual 3 onscreen buttons (back out, home screen and overview buttons) totally disappear and initially it appears that there is no way out of the app once you're in it. After an awful lot of prodding random bits of screen and in despair I was just going to reboot my phone when I noticed that pressing the power button not only brought up the shutdown dialogue but it also restored the onscreen buttons and I could then exit the app.
Once you know, it's not a problem but it looks like Neumann may have missed a GUI issue in the intervening years since they first issued this app.