How to find the key signature from video of a person playing.

[YammyFan]

Maybe, by looking at where the  KB player is putting his fingers it is possible to get a fair idea of the key he /she is playing in. But, I tried this and it is NOT all that accurate because sometimes accidentals are used when playing in the Key of C.. I know that some people have perfect pitch and that they would have no trouble recognizing the key signature of the song being played; but I wonder if mere mortals like me , are able to come up with the Guets are not allowed to view links. In order to access the links, please Register or Login way, to further interest in this topic ,would be to invite a member to post a video of themselves playing a song  showing their hands on their keyboard , and asking other members to guess what key signature. they are using.

[mikf]

You use your ears. You don't need perfect pitch. Play a few notes of the song on your keyboard. Then compare your playing to the  sound on the video. Doesn't even need to be a video, just a recording. Keep trying different keys till, they coincide. Shouldnt take more than two or three tries to get it right. If it is a video, you can also look at the lh chords on the video to help.
Mike

[ckobu]

Try using a chord tracker.
https://youtu.be/92aYTdA7tp8?si=OUIF-Mb7i8tFyOzo

[Robert van Weersch]

I don't have perfect pitch but just by trying, I'm always able to find the key signature within a few seconds.
Just try.

[mikf]

Agree Robert, you don't need perfect pitch just a feel for intervals, you play a couple of notes, move up or down a bit and get it by trial and error, as you say in a few seconds. You learn by just doing it, it's not hard.
Mike

[Toril S]

I can't always hear it right away just by listening, but by playing along with the song I find the key, no problem.