https://www.musical-u.com/learn/who-moved-the-tonic-part-1-hearing-key-changes/
If you’ve been working on playing by ear, you know that the tonic gives you most of the information you need to play a melody without written music. But what happens when the tonic changes? Enter the world of key changes!
https://www.musical-u.com/learn/who-moved-the-tonic-part-1-hearing-key-changes/