The app 'Audio FFT Visualise' written and published by Timo Rantalainen (tjrantal at gmail dot com) does not store any information about you persistently or share any information about you other than what is shared by the admob ads (I am unaware how much information is shared through the admob ads but clearly some because the ads are targeted to your phone). The app records your audio into memory for polyphony estimation for roughly 0.2 seconds at a time and discards the audio when the next epoch of audio comes in. The app never stores any of the recorded audio on the hard drive or otherwise persistently.