One of the most important skills you can learn with ear t…

https://www.musical-u.com/learn/how-to-find-the-tonic-of-any-song-in-a-major-key/
One of the most important skills you can learn with ear training is how to find the tonic of a given song or composition. Finding the tonic in sheet music is a fairly straightforward process; you have all the notes written out for you, and a key signature to help you out even further.

But what if you donโ€™t have sheet music? What about finding the tonic by ear?

https://www.musical-u.com/learn/how-to-find-the-tonic-of-any-song-in-a-major-key/