Wrote this as an explanation to someone but I thought it was an interesting topic so I would like to share it.
Episode 6 is about a boy named Wen who is trapped in a body that cannot age making him immortal in a sense but that’s to an extent not what ima be talking about. What ima be talking about is the harmonica which Wen always has throughout the episode. One of the songs played by a harmonica in Cowboy Bebop (soundtrack and all) is called “Digging My Potato” which serves as a way at presenting Wen with emotional decay and the harmonica being the instrument that represents his life (singular), Spike killed Wen with a gem tipped bullet which in a sense breaks the prison which imprisoned Wen. When Wen gets shot is on the verge of passing away he asks Spike a question that being “I feel so heavy, and yet, so at ease. Do you understand?” which Spike responds to with “As if” then Spike throws his harmonica into the air, mimes a gun with his finger and whispers “Bang” as it falls. This all reflects on what Spike told Faye as he left towards the end of the show he is actually haunted by the same “dream” like state as Wen who’s a man living in a past that won’t let him die. Now this is where I think this episode becomes a masterpiece (that is in reflection to Spikes conclusion), when Spike stands before the Syndicate in the end and says “Bang” before collapsing he is finally answering Wens question, ge now truly “understands” the relief he was talking about. Spike says one of his eyes “sees the past” like Wens eternal childhood, Spike’s life was a static loop of trauma. Shooting the harmonica (and eventually Vicious) show the violent act of breaking that loop to finally find rest (which he doesn’t actually achieve in ep 6) this is shown by the fact that Spike can’t play the harmonica. He cannot make music because he hasn’t yet found his own ending, he is still “carrying that weight”.