ok idk how much you pay attention to music in shows (music analysis is like my life lol) but like st literally does SUCH a good job w how they use music in the show... like california dreamin in 4x01 ?? when i first heard i was like oh lol bc theyre in california thats cool BUT the song is about running away to california when you're feeling sad and like....hellooooo....and then there's the fact that they chose the beach boys version instead of the original to allude to the 1980sness of it all. so cool
So, there are some key tracks from S1 and S2 that are repeated in S4V1 to show key significance or foreshadow things to come. For example, during Mike and El's fight, the track "eulogy" is played. This is significant because it was played over Joyce mourning Bob (a lost relationship) and Barb's funeral in S2/3. The fact this this track (albeit a revamped version) was the track chosen to play during Mike and El's fight is so interesting and really helps to show where their relationship is headed imo. Another track that's repeated is "on the bus" during Mike and Will's heart-to-heart after burying the body. This same track plays in S2 during Lucas and Max's heart-to-heart when they're kinda admitting their feelings--also, this talk really sets up their relationship, so that's foreshadowing to Mike and Will, lol. Also, "this isn't you" is repeated when Steve and Nancy talk in the Creel house. This track is used a lot throughout the seasons, but it's specifically tied to Nancy's guilt over Barb's death, as Barb tells her "this isn't you" before being taken by the demogorgan. Using this track in S4V1 foreshadows that Nancy still isn't over her guilt to do with Barb, hence her being tranced by Vecna at the end of V1. There's lots of other repeated tracks too, but I found these 3 to be the most significant <3