I've had plenty of reasons to get involved in audio production over the years, mainly for personal projects, and I've managed to pick up a lot of skill relating to the technical side of recording and editing audio. This includes not only things like using high pass filters or echoing effects, but also the way that different file types are optimized, and how to manage the quality of each file to make sure they're as small as possible without sounding tinny or warped.
I've had to create original music for many of my projects, a lot of which has never properly seen the light of day. Some of the albums I've not yet released are on indefinite hiatus due to a lack of certain tracks that I haven't yet completed. I occasionally go through and delete older music project that I'm not happy with, but I keep all of the music ready to re-upload if I ever get a chance to tweak it properly again.
Although MIDI files are quite an accessible filetype to work with, editing them is much more complex. Fiddling with the instruments is only a surface-level job, and there's a lot that can be done to adjust how they sound and progress, which alters the contents of the file in ways that can produce interesting and bizarre results.
Although they were never intended for any professional purpose, I spent some of my early teenage years creating "mashups" - multiple songs or audio sources mixed together into a single track, often using a specific track as a base and reworking the others around it. I created over 100 of these on an old YouTube channel under the name "mrtbrix" during my High School years, but stopped producing them once I got old enough to focus on more productive and professional pastimes