In addition to the previous video where I was explaining what does SINGING IN KEY mean, I chose to show you the difference between the same song sung in 2 different keys.
If you sometimes struggle for just 1 note in a song (too low, too high) that seems out of your reach, maybe* you should try to change the key of the song.
*it can be because the key is not right for you but also because you haven’t work out your voice enough at the extremities of your vocal range (low/high) and you need to practice more to be able to sing your whole range