Cool little feature, its not very accurate but as you say it will get you close, maybe enough to determine the key of a song. Nice Tut thanks!

The accuracy depends a lot on the articulation of the sound.

If you were to record your self humming a melody (hmmmmmm), it might not be as accurate as if you whistle or used a harder sounds like "laaaa" or "doooo". Fast attack strings might work better than slow attack strings, etc..

Also some sounds that might be pitch bent or have a wide dynamic range may not be as accurate.

Thank you so much NFX...