Ahhhhhh, post #5 helps me better grasp post #1s references to sort order of music within iMovie and FCP. There is the media chooser in those apps. If you (OP) want to keep trying to get that back to how you remember, you might want to
check the info here. I'm sure there's a similar bundle of "how to" for FCP too- just do a search.
I fired up FCPX, chose the music media chooser option and- for me- it is sorting by TIME (shortest to longest). I can click other options like Title, Genre, Artist to sort by those options (upper red box shows a few sort option)...
Right-clicking (or control clicking) on Music, displays the menu shown in the left of the screenshot, along with the "Sort Events by" option (lower red box).
Based on your description, Apple may have deleted some other sort options in some update of FCP or iMovie.
However, a workaround that may be much more effective at helping you quickly find what you want is do your sorts in iTunes or Music (much more flexible and easily searched too. You can sort by ANYTHING in those apps). Locate the music file you want, drag (a copy) out of iTunes or Music and into the video file clips browser (just like it is a video clip) and then put it where you want it in your Video Timeline.
In short: you can treat music files just like they are video clips. As such, you don't have to hunt within the (limited) media browser features inside of those apps. Use the much more flexible apps (iTunes or Music).