Tutuner — Pitch tracking tuner

Why another tuner app?
Other tuners uses some pitch detection algorithm which is just an *guess* the tone being played or sang.
This guess can be bad or alright, but it will always be just a guess.
This app shows real spectrum that is plotted into octave circle, meaning you can really *see* a note being played.
Note that overtones will be visible as well.
It's very responsive so you can use not only to tune an instrument, but also while singing or playing trumpet or violin.
There is a setting (in system preferences) to control how precise vs. responsive a spectrogram should be.