Here's a recommendation: create playlists, keep track of when you do so, and never delete them. I started doing this in 2011; 2 years and 45 playlists later I've decided to write about how this has affected me. This is more of a personal post than usual, but if you're interested in music and emotion then please read on.
I listen to a lot of music. I used to play the violin, but I gave it up when I started highschool. I was briefly attracted to the electric bass, but I never got any good. I had more fun repurposing an old radio as an amplifier head than badly covering The Beatles.
All of my friends and I actively listen to music. By this I mean that we seek out certain artists instead of settling for whatever comes on the radio. I started going to concerts my freshman year of highschool, stopped my junior year, and have just recently taken it up again. I've always listened to music while reading, working, writing, and programming. Especially programming — it's a great way to drown out the distractions of an open office, and because I make my living on the computer I spend a lot of time listening to different artists.
Certain songs mean a lot to me because of the context in which I first heard them. Guster will always remind me of my freshman year of highschool; Crystal Fighters reminds me of the summer; Arcade Fire's "The Suburbs" reminds me of my first serious relationship. I don't think I'm the only one who associates different songs or albums with different memories. I have no idea why it happens, but music seems tied to my emotions. When I listen to playlists I've made in the past, I feel how I did when they were created.
I've created about 2 playlists each month for the past two years, and each one has a specific date and a short description. Because I've done this, I can now "replay" my emotions at any time from that period, which I think is unbelievably cool. It's also been very cathartic — I can selectively return to a playlist I made while angry, or depressed, or elated, and reason about those emotions much more logically now that I'm removed from the particular situations by which they were triggered.
It's also fun to revisit the past, and to see how much my tastes and emotions have changed since then. I've spent the past year working in San Francisco, which has been hard because I don't have many friends my own age here (I moved from Philadelphia, and all of my highschool friends are attending college.) Listening to music that reminds me of my old friends and the times we've had together did a lot to help me adjust to my relatively lonely life here on the west coast.
Saving my playlists has been an interesting and overwhelmingly positive experience. I've found that I tend to feel the need for a new playlist every 2 or 3 weeks, but there's no hard rule. If you try this for yourself, be sure to write and let me know how it goes!