This is a question that comes up quite a bit. For Windows users, Audacity is probably the most likely app that will be used. Notably because it’s 100% free / opensource and is very powerful. Although you only need to know a few things about the app in order to quickly start editing songs or stringing them together into a single track. I created a somewhat basic tutorial (below) in my Pyro Workshop playlist in YouTube. During the COVID years, Cobra Firing Systems did some online training sessions as well showing people how to do some things in Audacity.
Audacity is also available for MacOS and Linux.
And for mobile platforms, I have ZERO clue. I would never consider editing music on a mobile device because of the fact that I’m an avid PC user. (I try to do as little as possible on mobile devices if the same thing can be done on a computer.)
For further discussions about Audacity, try hopping over to that specific subforum! (CLICK!)
Is there an app that you’ve found to be pretty helpful when it comes to editing audio?