I've just reached my passive long-term goal of 1000 songs in a personal Spotify playlist. This was done by simply adding newly discovered songs that I like and it took me more than 6 years (I'm quite picky).
Now if I look back on it, I have a date near each song indicating when it was added and the song evokes certain memories associated with it - where I was then, who I was with, what were the circumstances like, how I felt, etc. The emotional aspect is especially important for the memory to be vivid and a song does especially that - it serves as a physical equivalent for a particular emotional state.
So if I wanted, I could quite easily write up a sort of biography/sparse diary of those 6 years by following the playlist chronologically. What would be really convenient though, is having a possibility to add notes next to each song, upload pictures/videos from that time to make it a memory storing tool.
People usually gather pictures and sort them in folders or just keep them chaotically for this purpose. Being able to conveniently tidy things chronologically and have a digitally represented sequence of memories would add a valuable dimension to this. Also, few aspects (pictures, writing, music) would be combined to enrich the experience. This would turn the whole thing into a kind of personal biographical movie.
So all it would take is a simple extension to a music streaming platform that would let you do this. This could also be approached from a different angle, e.g. having a digital template that lets you store pictures chronologically in a list-manner and then adding notes and songs (if there were any favorites at that time) next to them, or alternatively one could start with writing. A list of favorite Youtube videos or any similar digital collection sorted chronologically can serve the same purpose.
The most convenient approach for a specific person would depend on what they continue doing on a daily basis without putting much effort into it. For people who are into discovering and collecting music, the playlist approach would be the best, for people who photograph a lot and collect pictures, it would be easier to add songs and notes to chronologically stored pictures (Instagram style), etc.
This is to an extent what social media does - yes, but it's not specifically designed for that purpose. If you could somehow isolate your Facebook or other social media posts done during a certain time period and then add "supporting material" to them to serve as memory collection, - that would be it.
Social media is also not very good for this, because looking back on one's memories is a very personal experience. Many would want to keep such a specifically designed memory list private (just like a diary). No one can experience your past looking back on your Facebook posts in a way you would.