Button1 changes function button2 - JS

sorry for my English. I am a Javascript programmer beginner.

My assignment is:
I have 2 buttons (button1, button2)
I need to create a condition (if / else).
If I click on button 1 it will play me song1
But if I click on button2, it changes the soundtrack on button1 from song1 to song2.

Please help me or write me if it is even possible to do it in JS. If this is not possible, please for some alternative to this assignment.
Thanks for the answers.