It’s usually one or two songs from a drama. But in terms of complete OST I will go with My Mister/My Ajhushi given how often I have listened to it and how long it has lasted in my playlist. I still listen to all the songs.

If we are talking about the whole playlist, that’d be Goblin hands down for me.

I'm not really an OST/music person. Like I could totally tune it and be completely confused when an OST is mentioned however there was one show that stands out to me: Gu Family Book. I really like the music in that show, particularly Only You by 4Men.

Honorably mention: I agree with @alathe about Hwayugi/A Korean Odyssey.

I tune out OST's for the most part. However there are some OSTs, where I have specific songs that I really like or remind me of the drama. Dream High, Healer, At Eighteen, and Our Beloved Summer.

I'm a sucker for OSTs, I'll cheat:
Jealousy Incarnate❤️❤️❤️
Nevertheless❤️❤️
Cheese in the Trap❤️❤️
(Also Just between lovers, Misaeng, My Ajusshi, IOTNBO and many more lol).
For instrumentals:
Falling for Innocence❤️❤️
My Ajusshi ❤️
Come and Hug me ❤️

I am a fan of k-dramas OSTs. My playlist is growing as I watch more series because I always add some of my favorite songs when I finish a drama.

So picking just one is extremely difficult. The above mentioned Hwayugi and Just Between Lovers OSTs are already in my list and now I'm really curious about Me too Flower OST but first I'll have to watch the drama (it's been on my list for a long time).

I'll have to pick two, I'm sorry XD
_ One drama for the songs: The best hit (I really love all of them, but my favorite ones are "Light in the sky" by Yoon Mirae and "Beautiful" by Glabingo and Punch).
_ One drama for the background instrumental music: Queen Seon Deok (the themes called "Dreams" and "On the edge of a precipice" are so touching).

"SECRET LOVE AFFAIR" made me love classical music.

Honorable mention: Almost every epic sageuks before 2020.
Chuno
QSD
My Country
Dae Jang Geum
Six Flying Dragons
Jumong
Shin Don
Faith
Rebel
Hwang Jini
Empress Myeongseong
etc

Some OSTs are really great that they stick in my head for a long time.
There's this one I heard in Kingdom of the Wind. The OST is centered on love between the Moo-hyul and lady involved in the love triangle with Do-jin. I can't really remember the tone. It comes and goes. But I do remember how it made me feel at different moments in time - sometimes peaceful or close to tears, sometimes crying actually, sometimes a good memory. It kinda slaps me that I do not recall the tone again. This tune once came into my mind in the examination hall.

Moving from this, there's an OST I got from Oh! Master - My Love By My Side by Kim Hyung-shik. I had already watched ep 6 and past it but the OST stuck right in my head. I had to comb (skim) haphazardly through 10 episodes of Oh Master so as to Shazam it out. It became the first full korean soundtrack on my playlist.

If I'll single out a drama with the best OST overall in the drama, I'll go with Curtain Call.

This is so hard,as a drama hoarder it's hard to actually choose 1 when u have more than 500 OST's LOL...Over the years i've realized i'm even more in love with the background aka BGM instrumentals than with the actual songs,as hits as they get and adore,the BGM always pull me more...
So i'd choose for starters Goblin for the OST and for the BGM,especially the unreleased ones(the iconic BGM of tragedy for the King and Queen),Secret,Gu Family Book,Forest Of Secrets,Six Flying Dragons,Signal/Tunnel,Hotel Del Luna,Vincenzo for it's epic BGM's,The Guest,Chicago Typewriter,Cruel City,Law School,Itaewon Class,King 2Hearts

Waow, it's hard!

I pick Goblin. I really liked the songs but the instrumental music too.

But I need to mention : Our Beloved Summer, Hotel Del Luna, Extraordinary You, She Would Never Know, Heartstring of which I listen to more than one or two songs.

This is a great thread! I was recently thinking during a rewatch of Just Between Lovers (which I'm still in the middle of), that the music there is so compelling and perfectly conveys the tone of the show, and that's why I don't rewatch some other shows as much (love Coffee Prince, but not that "la la la" song). I think My Ahjusshi has the best complete soundtrack, every song is great, from the soulful to the fun, but I'm going to pick Healer because every time I think of that show I hear "It's a beautiful feeling..."

The one that immediately popped into my head was HOTEL DE LUNA.

Ok, this is the hardest one of these for me so far. Immediately I'm trying to decide between Our Beloved Summer, It’s Okay to not Be Okay, Crash Landing on You, and Alchemy of Souls. This is not including the truly great individual songs on OSTs, of which there are so many. Even if I don’t love a soundtrack overall, every drama that I’ve watched has at least one song that I love somewhere in the mix. And I collect these into endless (ok, not endless, but seven so far) playlists that I listen to all the time.

BUT - this is no fun if I pick a million of them. So I’m going with It’s Okay to not Be Okay for sheer proportion of fantastic songs. When I compiled my favs out of this soundtrack, it was almost all of them. But not only does it have amazing songs that I listen to on repeat (shout out of appreciation to Janet Suhh who does so much to set the tone in the opening credits and elsewhere), but it also has themes for the main characters that it incorporates really beautifully into the drama. Kang-tae’s is mournful and tentative, Moon-young’s is mysterious and mischievous, and the brothers have one together that is sweet but sad.

If we were talking about instrumentals alone, my pick would hands down be Crash Landing on You. “Spring in My Hometown”, “The Season of Us”, “The Wind of the Day”, “The Song for My Brother”, “The Hill of Yearning”, “Time of Jeong-Hyeok for Se-ri” and so many others never fail to transport me right back to those scenes and those emotions. Nam Hye-seung and Park Sang-hee just really nailed it on this one. It feels like you're gazing out over a great and insurmountable distance, and it's just perfect.

But what if one of your favourite drama OSTs is from a drama you've never seen... How does that work then? 🤔

"You can only pick one drama with the best OST" implies your final pick is actually for the drama over the OST, no? 😂😂
I haven't seen My Country but its probably in my top 3 kdrama OSTs I'd actually buy... 🤣

But anyway... Genuinely actually couldn't pick just one lmao, I like music too much, but hard agree @alathe on Hwayugi having a fantastic OST.
Kinda seems superfluous to just list good OSTs since I'm not picking, but also, for ones not mentioned already, and overall OSTs not just single songs I play on repeat, Lookout, Beyond Evil, Weak Hero, Adamas, Prison Playbook,.

(and also every single Jannabi OST, ofc.)

My personal favorite and no 1, hands down: "You're Beautiful". Because it has 4 epically catchy vocal tracks. After that, the whole "It's Ok to Not Be Ok" truly is interesting and haunting, and Hotel del Luna and Scholar Who Walks the Night have my favorite BGM OSTs - the kind that I put on while I'm drawing or something. As for particular favorite songs, well, that would be a really looooong list.

For songs, I'd have to go with Oh Hae Young Again - I loved pretty much every track in that one. For instrumental music plus songs, probably Six Flying Dragons.

Oh dear, only one 🤧

I have to go with It's Okay That's Love. This is the first drama whose OSTs I listened to before I watched the drama (on Dramafever (RIP) 🥲) and fell in love with them before I watched the drama.

Honourable Mentions:

The Heirs
Heartstrings
My Love from Another Star
Crash Landing on You
Goblin

Getting beyond nostalgia favorites, the most recent drama I can think of whose mood was largely driven by it OST soundtrack was 'My Liberation Notes'. Lee Suhyun's 'My Spring', 'Deeply' by Hen, 'Laggard' by Shin Youme.

For an OST that literally drove the plot there's the drama 'When The Devil Calls Your Name'. I joked that the series was basically the 'Sondia Musical Hour' because al the songs were hers and I think the actress was lip-synching to her voice too.

I haven't seen them mentioned yet so I'll add Descendants of the Sun and What's Wrong with Secretary Kim. Both have incredible ballads that stay with you for a long time.

But if I had to pick only one I'd pick Reply 1988. I can listen to Lee Juck's version of Don't Worry Dear on an endless loop.

“Girls’ Generation 1979”. There are a handful of new songs, some excellent background music, and snippets of older songs from the 1970s and earlier.
But the older songs are chosen tastefully to fit in with the aesthetic of the drama, and it avoids the trap of being a “greatest hits of the era” OST.
For me, GG79 has the best use of music in any Kdrama. The OST enhances the endless rewatchability of every episode, and imprints scenes onto your mind forever. For example, check out the BGM in the “CPR” scene towards the end of episode 2, as sunshine sparkles on the water behind the characters - it’s beautiful.

Ughhh SOOO MANY....I'll just list all that come to mind, in no particular order:
Because This is my first life - all of them ig
Pray - Klang (Angel's Last Mission: Love)
Oh My Angel - CHAI (Angel's Last Mission: Love)
Like a Fool/Fate - Seo In Guk (Love Rain)
Love Rain - Jang Geun Suk (Love Rain)
Where is Dream/Han Ji Pyeong song - 10 cm (Start-up)
Day & Night (Start-up)
I'll leave you - Lee Sun Hee (Red Sleeve)
Windflower - Lee Sun Hee (Legend of the Blue Sea)
Our Beloved Summer, Scarlet Heart Ryeo (most of em)
It's okay that's love - Davichi

Yeah nah I’m not gonna just choose one

Any OSTs that Tearliner produces:
Coffee Prince
Heart To Heart
Cheese In A Trap
Love Alarm

Others OSTs I love:
Chuno
Shopping King Louis
Our Beloved Summer
Dream High S1

For Japanese:

Makoto Shinkai & RADWIMPS OSTs collaborations always slap:
Your Name
Weathering With You
Suzume

While definitely a problematic classic, listening to the Hana Yori Dango OST always transports me back to my youth

Similarly, with the opening song Sailor Moon and for the first Fruits Basket anime adaptation as well

Also the the heart pumping first opening song for Attack On Titan

All the OPs & EDs songs for Fullmetal Alchemist: Brotherhood (tho the first opening song remains my favourite)

And I love the classic anime Honey & Clover OST as well

There are obviously many many more but these are what I remember from the top of my head at the moment

The soundtrack for When the Camellia Blooms I found very appealing, from the quirky intro (Bloom). The songs were appropriate for the scenes. My favorite is Loser, played when the landlord finally lands the lawyer on the couch. And the song played when Dongbaek finds the flower strewn path, Like A Heroine in the Movie by Punch.

Are we talking about instrumental or vocal tracks?
Best instrumentals:
Secret Love Affair
Chuno
Rebel: Thief Who Stole the People
Money Flower

Best vocal tracks:
Days Without Tears (Mr. Sunshine)
Adult (My Mister)
Breath (It's Okay To Not Be Okay)
Drench (Rebel Who Stole the People)

And that is just scratching the surface of Kdrama soundtracks...

Task failed successfully everywhere in this comment section lol. It's just an OST gush thread 😂
Can you blame us though.

I started my own playlist with kdrama soundtracks on Spotify. It is called Kdrama Awesomeness.

I guess no one mentioned Chief Kim...

Everyone's already mentioned Goblin and Crash Landing on You which are my top picks too, so here's third on my list: Doom At Your Service!

The show might've been disappointing but the OST was anything but! Featuring Ailee, TXT, SIG, Davichi, Baekhyun - A SOLID line up with great songs! Even the instrumentals were goosebump inducing, like Doom's theme (it's the song you first here at that scene when he stops the truck from hitting PBY in ep 1 or something).

I think that the dramas with the "best" OSTs are the pop culture dramas whose OSTs swept the music charts, are instantly recognizable when they're referenced in shows, and become classics. Like Descendants of the Sun, Reply 1988, Goblin, My Love from the Star, or throwback Boys Over Flowers.

Now THIS is my alley.
Agreed about HAPPINESS--that intro OST jump starts my heart every time I hear it.
Now I need to check out ME TOO FLOWER--Yoon Shi Yoon and a fantastic OST?!
I am always listening for well done scores and OSTs. Kdramas can overuse OSTs or use them choppily, and worse, willy-nilly.
So, I take note I when the OST's are integrated into the drama smoothly AND when the OST enhances the story. Two dramas come to mind right now that do this.
Our Beloved Summer
A Moment at 18

A Moment at 18 surprises me because most of the ost is score not vocal music, and when vocal music is used it is effective. Our Beloved Summer's OST is brilliant at creating the mood of the story.

I don't even have to think about this, it would be hands down Goblin.
The most beautiful ost, Stay With Me is so iconic and has the highest views on you tube of any kdrama ost -https://www.soompi.com/article/1549318wpp/exos-chanyeol-and-punchs-stay-with-me-from-goblin-becomes-first-k-drama-ost-mv-to-surpass-400-million-views. When I listen to any songs from the ost it's like being comforted by an old friend.....sigh.

Well it wouldn’t be me if I didn’t say My Lovely Samsoon! But seriously, the OST mostly by Clazziquai was a revelation that I still listen to. I even learned the piano versions of the bgm and my aunt asked that the piano version of Over the Rainbow be played at her funeral ❤️

Empress Ki and Arang and the Magistrate both had glorious scores. Most of Empress Ki’s pieces are on youtube (single composer, Kim Jangwoo) but score music from Arang is hard to find. Among the songs, I love Park Wankyu’s The Wind and Ji Changwook’s Butterfly from Empress Ki.

My one pick would be Reply 1988. All the old songs in the OST, especially Hyehwadong both the original and the remake. Don’t you agree, @Reply1988?

Through a current show, The Eighth Sense, I found a great K-indie band called Wetter and a downtempo electronia band called Unalaska whose album Full Circle I listen to daily.

For the entire album/drama, no contest for me, it is Mr. Sunshine with all the hauntingly beautiful violin sounds. I still tear up when I listen to Elaine's Sad March and Park Hyo Sin's The Day.

For LSS inducing OST songs though, my runner-up is Goblin. "🎶 it's a beautiful liffeee🎶.

Yumi’s cells, is the one with the most songs with lyrics. Usually though, I only download one or two songs from OST’s usually the background music and the main love song. These are the key songs that instantly take me back to that drama and the mood it created. Twelve nights and I will come to you when the weather is fine are the OST’s albums I have the most background music tracks.

I love listening to OSTs especially the emotional, heartbreaking ballads.

My main picks have already been mentioned: Goblin & Oh Hae Young Again. I still listen to them to this day!

Oh my gosh, I love Happiness, but I can't think of any particular song right now. Need to go look it up!

I'm gonna indulge in this thread and go off topic even more, to talk about random OST things not related to the challenge:

Does anyone else collect songs with the same title? I mention this because there are a vast number of kdrama OSTs called "Stay" or close enough, (or occasionally it has it in the hook but not the name like Dimly by RIO from Red Sleeve), and I do do that, and have an entire playlist of songs called Stay, or that invoke the feeling of Staying.
I make these with other words and songs too, just that that one is like 91% OSTS so is more relevant to this thread lol.

The other thing I do, or rather my brain does, I don't always have a choice in the matter, is connect or pair songs by random associations. Again, not limited to OSTS, but, like,
The Giving Tree (Lee Seung Yoon, from OBS) + The Longing Dance (Ji Eun Lim, from Are you Human Too).
or
The Story that Won't End/ 끝나지 않을 이야기 (Skidz, Extraordinary You) + Sorry (2F, Run On), because there is something about their keys and or their chord progressions or something music theory related that my brain can hear but doesn't know enough about to recognise, that means my head plays them on loop constantly.
(Ironic considering the titles. The Story that Won't End: Sorry. 😂)

I am also curious if there is anyone else who has examples of parts of the music of a show that never make the official soundtrack, but that haunt you for the rest of your life. This is often random parts of the background music, that I can never find, or versions of other songs (often classical pieces, but one time it was a Chinese version of Dream by the Cranberries) made just for the show, or merely a riff that lingers in my head but fades from memory at the same time, always slightly out of reach.
Like the version of The Synchopated Clock that is used in My Fellow Citizens over the restaurant fight scene in approx Episode 3 that took me ages to find, (or every time Carmen is used, but that one is super recognizable, so doesn't really count).
Two Folk examples related to this are,
The haunting children's version of part of The Gatekeeper Song (Ganggangsullae) in Tale of the Nine Tailed which gets stuck in my head all the time, and then the Salamander Rain Ritual Song from Lovers of the Red Sky which I haven't been able to find anywhere. I can remember the lyrics though and I know what they mean!

This is unfair, how can I choose only one?((( My collection is full of OSTs, including instrumentals, songs from the shows I dropped and even those I never watched... It's that bad, yes. Can you pick just one ingredient to eat for the rest of your life? No, because you'll eventually get sick and die from malnutrition then. That's me with music. I'm greedy and I refuse to be tortured like this)))

Always and forever, Goblin. From Ailee, to Mamamoo, to Roy Kim and just the soundtrack BGM themselves, nothing really has captured my heart the same. The only OST I’ve actually bought the CD for. And the only soundtrack I learned music to play. 😆

My vote goes for Chicago Typewriter especially Satellite Love, Come with me, Time walk and Writing our stories.
Honorable Mentions
Hotel Del Luna
Hwarang
Goblin
Find me in your memories
The Heirs
You are Beautiful

I watched dramas for the plot and normally will not pay much attention to the music. However there are a number of dramas with great music that struck a chord in me and remained deeply rooted. Having to pick one will be doing injustice to the rest, but since this topic is picking only one sound track, I would say Agency and the opening theme song sung by Kim Pu Reum titled Never Let Go.

Without a doubt, Because This Life is Our First for me. It’s like the songs (two at least) were created from the OTPs perspectives. Shelter for Ji-ho and Marriage for Se-hee. Not to mention the songs have really beautiful melody and meaning. It will always be my favorite, the OST. And the drama. And the characters. ❤️

Huh, nobody has mentioned Bossam: Steal the Fate or Age of Youth yet. Well there you go, I have now.