Tonscape is a precise sine-wave tone generator and real-time spectrum analyzer in one app. Dial in any frequency your device can produce — 0.01 Hz to ~24 kHz — typed or swept, then prove it: the mic analyzer shows a live FFT with peak-hold and whether a frequency is present above the noise floor. Great for testing speakers, headphones and subwoofers, tuning and audio education. Pro ($0.99 one-time) adds binaural beats, white/pink/brown noise, nature sounds and a sleep timer. No tracking.