Editor's Note: The following contains spoilers from Episode 9 of The Last of Us.Music has always been a key component of The Last of Us. Both games are heavily infused with good stuff, going way beyond Gustavo Santaolalla's awesome theme score, so it couldn't be different with HBO's series adaptation. During Season 1, the show has graced us with great songs in some of the most crucial moments, and they are never music just for the sake of music.

Every song is directly connected to the story being told in their own episode, and, therefore, they are each uniquely important. The series premiere, "When You Are Lost In The Darkness", for example, has a whole segment set in 2003, and music is a big part of how that ambiance is built - it was another time, so the songs have to reflect it. So let's dive in all of those musical references, shall we?

Avril Lavigne — "Tomorrow"

After Sarah (Nico Parker) wakes Joel (Pedro Pascal) up in the series premiere, she cooks breakfast for them in the kitchen. The song playing in the background is Avril Lavigne's "Tomorrow", from her 2002 album Let Go. Although not a hit like "Complicated" and "Sk8er Boi", "Tomorrow" is perfectly on tune with the premise of the episode. The singer is insecure about her relationship, asking her partner to give her more time to be alone. She is not sure how she will feel the following day, and wants to believe her partner when they say it's going to be okay. Sadly, we know Sarah won't have a "tomorrow", as she dies later in the episode. Her father repeatedly tells her it's going to be okay, that they will survive, but she doesn't. The whole world could have more time, too, but the cordyceps doesn't wait.

Dido — "White Flag"

Once again in the breakfast scene in the premiere, but now playing when Tommy (Gabriel Luna) joins Joel and Sarah - whose track selection is killer, we must say. Dido's "White Flag" was constantly played in the radio (remember radio?) in 2003, and there was no escape. The lyrics tell of a lover in regret of their actions, asking their partner for another chance. They understand the damage that was done but they know their feelings are true. This foreshadows how Joel will come to feel about his past. He is aware he wasn't a good father for Sarah, nor a good brother for Tommy, although he loves both of them still, even after the world has ended. He's at war with his past and doesn't plan on letting it go - no white flag above his door.

Depeche Mode — "Never Let Me Down Again"

80s means trouble. It also means it's not 2003 anymore, as the premiere episode moves to 2023. As Joel, Ellie and Tess (Anna Torv) venture out of Boston Quarantine Zone, the radio in their apartment comes alive with "Never Let Me Down Again", by Depeche Mode, which, according to the smuggling code they've established will Bill (Nick Offerman) and Frank (Murray Bartlett), means there's trouble around.

Lead singer Dave Gahan originally wrote the lyrics about his heroin addiction, depicting the ups and downs until sobering up. In The Last of Us, Craig Mazin explains it's about Ellie going on a journey with Joel, who's a dangerous man. They don't know it, but they will become each other's best friends, and are surely going to let each other down along the way.

Fleetwood Mac — "I'm Coming Home To Stay"

On to "Long Long Time", the emotional third episode. For a while, it takes us back to 2003, when we meet Bill. He's hiding from FEDRA agents in the bunker beneath his mother's house and only comes out when he's sure the goons have left. That's when the party starts for him, to the tune of "I'm Coming Home To Stay", by Fleetwood Mac, back when it was a blues band led by Peter Green. The singer talks of going back home and never leaving again. Well, Bill is beginning his coming-out process and allowing himself to be fully visible after a whole life of hiding, and he doesn't plan on leaving.

Cream — "White Room"

Still in Episode 3, but now in 2007, Bill is still living by himself. He's a lonely person, he just doesn't admit it to himself. Working in his bunker, he's listening to "White Room", by Cream, which is ironic because he is in a pretty dark room, actually. The song talks about a person waiting for someone on a train that's never going to arrive. A bunker is also a room "where the sun never shines", where Bill watches "shadows run from themselves" (aka the Clickers) on his CCTV cameras. Also, "White Room" came out in the 1960s, which, according to the smuggling code, means "no new stuff". Bill was stagnant, making no progress in his existence and being the same lonely person he always was. Until...

Linda Ronstadt — "Long, Long Time"

Until a song from 1970 came with new stuff to set Bill free. "Long, Long Time", by Linda Ronstadt, is now a classic thanks to The Last of Us. It represents the many barriers Frank overcomes to touch Bill's heart after they meet in 2007. In a recent interview, series co-creator Craig Mazin revealed what drove him towards this song: it had to be incredibly sad, about yearning for love, while never getting any, and coming to terms with the fact that you will always be alone. That is the description of a lonely person, who, in this case, is Bill, yearning for love without the prospect of ever getting any, due to the constant repressing he had to put himself through as a closeted gay man. Fortunately, he eventually found love. Fortunately for us, we got this beautiful song back.

RELATED: 'The Last of Us': How Is Ellie Immune to Cordyceps?

Max Richter — "On The Nature Of Daylight"

Yes, you know this one. Max Richter's "On The Nature of Daylight" was already a modern classic even before it was featured in The Last of Us. You probably heard it before in movies like Shutter Island and Arrival, or the hit TV series The Handmaid's Tale. Here, it plays as Bill and Frank enjoy their last day together and get married, with its melodic overtones making the scene even sadder for us.

Erasure — "Chains of Love"

When Joel and Ellie enter the bunker at Bill and Frank's compound, there's still 1980s songs playing on their radio - at that moment, "Chains of Love", by Erasure, is on. Not much is going on then, and the singer speaks of not letting yourself be caught in "the chains of love", meaning that true love is one that should set you free, and not make you feel chained. Kind of like what Frank's love did to Bill, right?

Hank Williams — "Alone and Forsaken"

Episode 4, "Please Hold To My Hand", is where Joel and Ellie's journey through what used to be the USA really begins, as they leave Bill and Frank's compound behind and hit the road. After Ellie teases Joel with a male magazine, she finds a cassette tape with songs by Hank Williams, which Joel claims to be from "before his time". The song they play is "Alone and Forsaken", which works as a perfect analogy to what happened to the country after the cordyceps outbreak, now a wasteland that's "alone and forsaken by fate and by man". The name of the episode also comes from a verse in this song, the pleading in the end: "Oh Lord, if you hear me, please, hold to my hand. Oh, please, understand."

Lotte Kestner — "True Faith"

The end credits of Episode 4 actually bring an interesting Easter egg for the sequel to the original game, The Last of Us Part II. Originally released by New Order in 1987, "True Faith" is part of the sequel's soundtrack as a theme for a grown-up Ellie, sung by Lotte Kestner in an acoustic cover. In the game, the song represents her growth after the whole journey she goes through, a painful process through which she finally becomes an adult. In the series adaptation, it brings the aggravation of being a 1980s song, and we know it to mean there's trouble ahead for our heroes.

Jessica Mazin — "Never Let Me Down Again"

In the end of Episode 6, Joel is wounded by a group of raiders as they flee from the university campus, and collapses on the ground after they leave the city. As Ellie desperately attempts to reanimate him, a beautiful version of "Never Let Me Down Again" comes on. This time, the Depeche Mode is sung in an acoustic version by Jessica Mazin, showrunner Craig Mazin's daughter.

In the The Last of Us podcast for the series, Mazin explains he asked her for "a haunting and slow, and about a daughter mourning the loss of her father," a direct contrast to the first time this song was played, in Episode 1. Back then, they were setting out on their journey together, each with their own baggage, hoping they wouldn't be let down. Now, Joel has let her down, and Ellie needs him more than ever to not let her down again.

Pearl Jam — "All or None"

Pearl Jam may be one of the best rock bands active today, but in The Last of Us, their career ended in 2003 with the cordyceps outbreak. They had time to release Riot Act, their 2002 album, though, where "All or None" is. The song plays in the beginning of the flashback sequence in Episode 7, "Left Behind", showing us Ellie's days before setting out of Boston QZ with Joel and Tess. Back then, she endured constant bullying at school and had no friends, with her best friend Riley (Storm Reid) having vanished without a trace three weeks earlier. Alone, she firmly believes hers to be a "hopeless situation", like the one the song mentions in the lyrics.

A-ha — "Take On Me"

The importance of A-ha's "Take On Me" in The Last of Us can't be overstated. It was already in the trailers for Season 1, and we finally got to hear it in Episode 7, when Riley shows Ellie how wonderful escalators really are. This song is perhaps the defining song for Ellie's whole journey throughout the franchise, from bratty young teenager to strong and determined woman. It also plays a huge part in the sequel game, The Last of Us Part II, with a beautiful acoustic cover performed by Ellie's original voice actor, Ashley Johnson.

The Cure — "Just Like Heaven"

Yes, this is a version for babies of "Just Like Heaven", a classic The Cure song. It plays as Riley shows Ellie the merry-go-round during their adventure in the mall inside Boston QZ. Why not use the original version? Because it would sound weird in a kid's ride, wouldn't it? Plus, it's the perfect song to describe the feeling between Ellie and Riley - it sounds just like falling in love. The lyrics (which we don't hear, unfortunately) are also perfect for the characters, who are realizing their who they really are to each other, as Riley shows Ellie the wonders of the mall ("Show me how you do that trick / The one that makes me scream, she said / The one that makes me laugh, she said") in their last night together, after Riley vanished for three weeks and before she moves to Atlanta QZ with the Fireflies ("Why are you so far away, she said / Why won't you ever know that I'm in love with you?").

Etta James — "I Got You, Babe"

Nothing against Ellie's music taste, but she was desperately in need of new music in Episode 7. That's what Riley provides in their scene in the Halloween store inside the mall, showing her how good Etta James is with "I Got You, Babe". At that moment, they are already aware that that will be their last night together, but choose to enjoy it. The lyrics reflect a relationship that has endured good times and bad ones, too, but gets over them together - how relationships in general should be, right? It's in that scene that the girls share their first kiss, too, after dangerously dancing on top of the glass counter.

A-ha — "The Sun Always Shines on TV"

Yep, another A-ha song. This time, it plays after the opening credits on the season finale, "Look For The Light", but not how you might expect. It's the song Anna (Ashley Johnson) sing to her newborn daughter, Ellie, after they both survive a Clicker attack while Anna was giving birth. Marlene (Merle Dandridge) finds the two of them, as Anna lulls Ellie to sleep singing "The Sun Always Shines on TV", showing that A-ha runs in Ellie's blood. The music video ends with singer Morten Harket becoming a drawing and being forced to leave his loved one, much like Anna, who was bitten by the Clicker, is forced to leave her daughter before turning into a Clicker herself.

Gustavo Santaolalla — "The Path (A New Beginning)"

In Episode 6, "Kin", Joel and Ellie finally find his brother Tommy living in a commune in Jackson, Wyoming. The dynamic duo has a fight the night before leaving for the University of Eastern Colorado. They know they now share a strong bond but are both afraid of what it might do to them since both have endured so much loss already. In the end, they make up and head to the university together, accepting their roles in each other's lives and their father-daughter dynamics. "The Path (A New Beginning) is a song by Gustavo Santaolalla, and is part of the original game soundtrack, bringing a hopeful feeling as Joel and Ellie go on their path together. The song is also the closing song of Season 1, playing when Joel and Ellie arrive in Jackson and over the credits of the last episode, "Look For The Light". Even after everything that happened in Salt Lake City, this song still manages to make the season end on a hopeful note.

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