Go to www.hooktheory.com

Switching key of a section while another is playing will cause that section to play

Let’s say you have a theorytab with a verse and a chorus. If you play the verse and change the chorus to Locrian then the chorus will play

not only this, but scrolling down to an unloaded section of a theorytab will cause that section to play as well (notably, at the same exact point in time as the other one was on)

can get pretty bad on songs with a ton of sections such as in the vid below

https://streamable.com/1gwpw8