Detect audio frequency

For a small desktop project (MacOS) I need to be able to detect the frequency of sound.
Are there any people out there who have accomplished this in the past?

I simply need to be able to whistle or hum a melody and detect the frequency of the individual notes.
(Either through plugins or Declares)

I played with Accelerate and Fourier Analysis on macOS via Declares. So yes.

I looked up some stuff about “Fourier Analysis”. I must say that I don’t know where to start. What did you find out while playing around with that?
Will it be able to detect frequencies in real time? I noticed an old topic here on the forum, where they talked about a guitar tuner. But I never saw anything that could help me a bit further.

That you can build a real-time analysis (and even display) tool that you could use to read the main frequency/ies of a sample (which can consist of real-time data too). It’s not that complicated. I’ll try to dig up the code.