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Frequency

A tone generator and a set of ears. Play a frequency, or measure the one already in the room.

€6.99v1.38mic only, no internetapp.freq.gen

Add Frequency to my suite Take all ten — €30

What it does

Sine, square and triangle at any frequency, plus binaural and isochronic modes
Libraries built in — Solfeggio, Rife, Schumann, planetary, chakras, brainwaves
Musical notes at Concert A, Scientific C, Otto 128 or Megalithic tuning
Tuner with pitch detection, FFT spectrum, and a sound-level meter

Microphone only, and no internet. The mic feeds the tuner and the level meter in real time. Nothing is written to a file, and with no network permission there is nowhere to send it even if there were.

What it can reach

This is the whole list. Android prints the same thing under Settings › Apps › Permissions once the app is on your phone, and it was not written by us — check one against the other.

Microphone	The tuner and the level meter read it live — nothing is recorded
No internet permission	Nothing measured can be sent anywhere

Android 8.0 and up. Bought once, yours to keep: no account to make, no subscription, and no upgrade screen inside the app — the key you buy unlocks it and every version after it.