Why do we need a header file? And why multiple ".cpp" files for every project?

[adamwilson]

Actually I originally started doing it after a comment from Jules on a similar question I put on the forum a few years ago.

AudioLiveScroller.h - is there a reason why no CPP file?

It makes no semantic difference whether a class is written inline or not. But whenever you have a simple class that can be written as header-only, I'd always recommend doing so. It means there's less code, less boilerplate, and all the code for that class is in one place.