FFTWave

App is very intuitive and free. It shows numerical values of frequency of peeks. However, the value is not super accurate. For example, the middle A sound is 440Hz. The app shows 441.4. And it’s happening on both my iPhone and iPad. So it’s very unlikely due to the microphone.

There are no ads you have to worry about with this app, it’s very straightforward to use, and it works exceedingly well with external audio interfaces like my IK Multimedia iRig 2, which is typically used with guitars and other musical instruments. Perfect for those of us who still like to repair tape decks, where precise frequency readings are essential, especially for motor speed and playback head azimuth adjustments. The app was definitely a big help for replacing the belts on my Sony cassette deck from 1996. 👍

A little tweaky in resizing bandwidth but VERY straight forward and very useful for live sound control. No ads.